Transportation Planning for Your Community:
Monitoring & Forecasting1980
Click HERE for graphic. PREFACE This publication is part of a series entitled Transportation Planning for Your Community and is designed to acquaint officials and planners with transportation planning for communities of from 25,000 to 200,000 population. The series consists of two guides that explain the concepts of trans- portation planning and five technical manuals that describe techniques for carrying out transportation planning programs. The guides are: A Guide for the Decisionmaker and The Manager's Guide for Developing a Planning for the Decision Program. The five technical manuals are titled: Traffic Planning Transit Planning System Planning Monitoring and Forecasting Programming Projects A Guide for the Decisionmaker describes the importance of urban transportation and the benefits of transportation planning. It includes a review of how transportation planning works, and the role of city, county and town officials in transportation planning. The Manager's Guide for Developing a Planning Program describes the principles of transportation planning and is directed to those engineers, planners and administrators who are charged with the responsibility of organizing and administering the transportation planning program. The individual technical manuals describe transportation planning techniques appropriate for small communities. The manuals also include references to other publications that describe appropriate planning techniques. The Traffic Planning manual is a reference of basic traffic engineering techniques and their potential for improving traffic flow and traffic safety of urban arterial streets and highways. The manual identifies the traffic engineering measures appropriate for consideration in development of transportation improvement plans and programs. The Transit Planning manual includes techniques for estimating transit patronage, service options, and operating requirements. Also included are procedures for evaluating the need for specialized services for the elderly and handicapped. i For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 The System Planning manual details the steps required for the functional classification of streets and highways, the estimation of future traffic, the estimation of the impacts of future traffic, and the estimation of street and highway system requirements. An Appendix includes alternative methods for forecasting traffic. The Monitoring and Forecasting manual provides instructions for assembling inventories of transportation and land activity. It describes methods for monitoring the performance of the transportation system and general community development and methods for forecasting information needed in urban transportation planning. The Programming Projects manual contains procedures for development of the transportation improvement program. Included are procedures for identification of candidate improvement projects, determination of the plan to fund candidate improvement projects, assignment-of priorities to candidate improvement projects, budget allocation and project scheduling, and monitoring, adjusting and evaluating the programs. This series was prepared by the COMSIS Corporation and the Highway Users Federation for Safety and Mobility under a grant from the Federal Highway Administration with the aid of a "steering committee" made up of the following officials: Dan C. Dees Illinois Department of Transportation Springfield, Illinois James Echols Tidewater Transportation Commission Norfolk, Virginia David D. Grayson Automobile Club of Southern California Los Angeles, California John J. Holland Cumberland County Planning Board Bridgeton, New Jersey F.W. Landers Department of Public Works Worcester, Massachusetts Marion R. Poole North Carolina Department of Transportation Raleigh, North Carolina ii The principal investigators were: Arthur B. Sosslau COMSIS Corporation Wheaton, Maryland Marshall F. Reed, Jr. Highway Users Federation for Safety and Mobility Washington, D.C. Other principal authors were Maurice M. Carter of COMSIS Corporation and Woodrow W. Rankin of the Highway Users Federation. iii TABLE OF CONTENTS Page PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 CHAPTER ONE: INVENTORIES. . . . . . . . . . . . . . . . . . . . . . . 3 Street and Highway Inventory . . . . . . . . . . . . . . . . . . . 3 System Mileage. . . . . . . . . . . . . . . . . . . . . . . . . 3 Physical and Operating Characteristics. . . . . . . . . . . . . 4 Travel Characteristics. . . . . . . . . . . . . . . . . . . . . 4 Inventory of the Public Transportation System. . . . . . . . . . . 8 Inventory of Land Activity . . . . . . . . . . . . . . . . . . . . 9 Analysis Areas. . . . . . . . . . . . . . . . . . . . . . . . . 9 Land Use Data . . . . . . . . . . . . . . . . . . . . . . . . .12 Population and Household Characteristics. . . . . . . . . . . .12 Employment Data . . . . . . . . . . . . . . . . . . . . . . . .14 CHAPTER TWO: MONITORING . . . . . . . . . . . . . . . . . . . . . . .18 Establishing A Monitoring Program. . . . . . . . . . . . . . . . .18 Monitoring for System Performance . . . . . . . . . . . . . . .18 Monitoring to Update Inventory Information. . . . . . . . . . .20 Scheduling of Data Items to be Monitored. . . . . . . . . . . .20 Monitoring Travel Data . . . . . . . . . . . . . . . . . . . . . 22 Roadway Data. . . . . . . . . . . . . . . . . . . . . . . . . .23 Public Transportation Data. . . . . . . . . . . . . . . . . . .23 Monitoring Changes in Land Activity. . . . . . . . . . . . . . . .26 CHAPTER THREE: FORECASTING. . . . . . . . . . . . . . . . . . . . . .29 Population and Dwelling Unit Data. . . . . . . . . . . . . . . . .29 Mean Household Income. . . . . . . . . . . . . . . . . . . . . . 30 Phase I Mean Income Estimation . . . . . . . . . . . . . . . .31 Phase II Distribution of Households by Income. . . . . . . . .31 Auto Ownership . . . . . . . . . . . . . . . . . . . . . . . . . .31 Employment . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 iv LIST OF FIGURES Figure Number Title Page 1 Monitoring and Forecasting Procedure. . . . . . . . . . . . . . 2 2 Potential Sources of Data..*..* . . . . . . . . . . . . . . . .19 3 Typical Load Point Check Form . . . . . . . . . . . . . . . . .25 4 Typical Transit Ride Check Form . . . . . . . . . . . . . . . .27 5 Distribution of Households Based on Average Income Per Zone . . . . . . . . . . . . . . . . . . . . . . . .32 LIST OF TABLES Table Number Title Page 1 Number of Suggested Analysis Areas. . . . . . . . . . . . . . .10 2 Sources of Land Use Data. . . . . . . . . . . . . . . . . . . .13 3 Recommended Stratifications of Household Income. . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 4 Employee Rates By Land Use Type . . . . . . . . . . . . . . . .16 5 Suggested Monitoring Schedule for Communities Experiencing Moderate Growth. . . . . . . . . . . . . . . . . .21 INTRODUCTION This manual describes procedures needed to forecast and monitor transportation related characteristics. Forecasting includes estimations of future population, land-use and economic characteristics for both the community and the traffic analysis zones within the community. Monitoring is an assessment of whether forecasts and resultant travel demand estimates are achieved. A baseline inventory of existing conditions is important for both forecasting and monitoring, and communities need to establish such an inventory from which to launch a continuous transportation planning program. The transportation related characteristics that need to be forecast are those that influence travel and that are required for transportation system planning. Other information needed for transportation planning purposes other than for monitoring and forecasting are discussed in the Traffic Planning, Transit Planning and Programming Projects manuals. The major purpose of monitoring is to determine if development trends are evolving as forecast. If major discrepancies between actual and forecast change are found, the forecast transportation related characteristics may need to be reviewed. The monitoring program also keeps the base inventory up-to-date. Initially, the following transportation related characteristics necessary to evaluate whether development and travel demand trends agree with forecasts should be monitored: - Traffic Volumes - Transit Patronage - Dwelling Unit or Population Changes - Changes in Total Employment - Changes in the Transportation System (additions and/or deletions) In many situations, analyzing and projecting basic inventory items, such as traffic volumes and transit patronage, will be sufficient to identify problems and to plan improvements. In communities where annual travel and population growth rates are less than two percent, monitoring should be limited to population and traffic, in addition to discussions with elected officials, the public, and professionals in local area departments (i.e., public works, police), to determine transportation problems. It is recommended that monitoring in greater detail than discussed above not be done unless the trends observed indicate a divergence from anticipated trends or unless the basic data needs to be updated. The recommended updating is discussed in Chapter Two. Chapter One of this manual describes inventories required for monitoring and forecasting. Chapter Three discusses the forecasting required for system planning. The relationships between inventorying, monitoring and forecasting, as related to system planning, is shown in Figure 1. 1 Click HERE for graphic. Figure 1 MONITORING AND FORECASTING PROCEDURE 2 CHAPTER ONE INVENTORIES Three types of inventories are recommended as the basis for monitoring and forecasting. These are: - The street and highway system; - The public transportation system - Land use and socioeconomic characteristics, The street and highway system of an urban area is the focus of nearly all travel, both by private automobile and public transportation. The inventory includes the functional classification of the system as well as mileage, physical and operating characteristics and characteristics related to the volume of traffic. Public transportation includes the municipal bus system, taxicab and limousine service, local routes of interstate bus lines, school bus operations, transportation for non emergency medical service, and service for special programs such as the nutrition program for the elderly. Land use data are used for many purposes including transportation planning. Most urban area planning agencies will have land activity data. This information may need to be restructured for transportation planning purposes. Socio-economic data is available through census tabulations and can be augmented through local sources. Auto ownership information may be obtained from the motor vehicle administration. Personal income data exists in most State revenue office files. Inventory files describing land use and socioeconomic characteristics of an urban area may be found in agencies such as the planning and zoning office, employment security, tax assessor, State motor vehicle administration and, of course, the State transportation agencies. The time spent seeking available data can save many man-hours in the collection of new data. STREET AND HIGHWAY INVENTORY The following three categories of data are required as part of the street and highway inventory: - System mileage; - Physical and operating characteristics; and - Travel characteristics. System Mileage The first job is to establish the functional classification of the street and highway system. The functional classification process, discussed in detail in the System Planning manual, classifies facilities as follows: 3 - Major Arterials - Minor Arterials - Collector Streets - Local-Access Streets The first step of the street and highway inventory is to develop mileage totals for each category of functional classification, The mileage of Major Arterial, Minor Arterial and Collector classes is determined by measurement or from road inventory files. Local-Access street mileage is obtained by subtracting the total Arterial and Collector mileage from the total street and highway mileage measured, Freeway mileage should also be obtained as a separate category even though it is classified as a major arterial. Physical and Operating Characteristics Each roadway segment should be identified to complete the basic inventory. Data, such as lighting , jurisdictional identification, right-of-way width,, sidewalks, etc., can be appended to the records as required. Although not required for monitoring and forecasting, such information is required as described in the Programming Projects manual. Knowledge of locations with high accident rates will assist in later analyses. It is recommended that an accident data system be established to search out high accident locations, Major trouble spots should be identified and can be plotted on a base map of the study area. Travel Characteristics The first task of inventorying roadway volumes is to establish a traffic counting program. To begin, all roadways for which traffic volumes are collected by other agencies can be eliminated from this program. The remaining roadway segments should be included in the traffic counting program. Traffic volumes should be posted on suitable maps and included in the roadway segment inventory records. Reference 1 provides guidelines on developing an integrated urban traffic counting program. Methods commonly used for counting traffic are: 1) using an automatic traffic counter and 2) manually counting vehicles.2/ Automatic counters are generally used for counting total volumes (either in one or both directions). Manual 4 counting is best suited for short counting periods or when it is necessary to determine the volume of vehicles by vehicle type (e,g., cars light trucks, heavy trucks, etc,). Generally, volumes from automatic counters will satisfy the need in smaller urban areas, Automatic traffic counters may be borrowed from the State transportation agency. They record traffic volumes passing over a pneumatic hose in a set time period. The State transportation agency may have permanent count locations in the urban area. Counts made for several years are useful for a study of trends in traffic volumes. The time period for traffic counting is usually 1 hour, but equipment is available for shorter time periods. The analyst should be aware that shorter time periods will increase the amount of data and tabulations necessary to arrive at Average Daily Traffic (ADT) volumes. The counters assume one vehicle for every two actuations of the pneumatic hose, If the road segment carries a large number of multi-axle trucks, a correction should be made. Without correction, accuracies of 95 percent can be achieved. The objective of the counting program is to obtain an ADT volume of the roadway segment. In order to achieve the objective, it is recommended that a minimum of one midweek 24-hour count be taken. A 3- day count will produce greater reliability. For updating volumes, it is recommended that one 24-hour count be taken at least every two years. Along each arterial, not roadway section, a 7-day count is recommended each 2-years. Below is an example of how to obtain an ADT volume for a roadway segment: Given: 1. Three-day, 24-hour, weekday station counts of 8,465, 9,100, 8,755 vehicles per day in October. ` 2. Seven-day average daily volume factor, relating weekday to average week of 0.986 (measured by State transportation agency for similar arterials). 3. Month factor for October = .95 (areawide traffic volume factor from State transportation agency). Find: ADT of roadway segment: STEP 1: Average 24-hour volume from hose counts = 8465 + 9100 + 8755 -------------------------- = 8,773 vehicles per day, 3 STEP 2: ADT of roadway segment = observed travel x daily factor x monthly factor = 8,773 x .986 x .95 = 8,218 vehicles per day. 5 Thus, in the above example, the roadway segment ADT volume is 8,218 vehicles per day. The daily factor should be retained for future use when updating the roadway segment volumes. For some planning purposes peak and off-peak period traffic volumes may be required. These can be calculated from traffic counter recorded volumes. Another approach would be to utilize hourly factors available from other sources such as the State counting program. In addition to volume counts, it is also desirable to distinguish between through traffic (traffic that uses the roadway system of the study area but has neither a trip origin or trip destination within the study area) and local traffic. Observations suggest that through traffic becomes a lower percentage of total traffic as the urban area population increases. 3/ To distinguish between through and internal travel, it will be necessary to conduct a limited roadside origin- destination survey at the study area cordon. The roadside survey consists of stopping at least ten percent (20 percent is recommended) of all vehicles passing through the station for driver interviews and a traffic count of all vehicles during the survey period. 4,5/ After selecting the external cordon stations, each site will require a field reconnaissance to design a safe interviewing location. The location should be well signed for the motorists and designed tko minimize traffic delays. It is recommended that a law enforcement agency assist in stopping traffic to be interviewed. The public is more responsive to a uniformed officer. One of the following two questions should be asked of each motorist: - For trips entering the study area: "Where are you going?" - For trips leaving the study area: "Where are you coming from?" If the place is inside the study area, the answer should identify the actual address or the closest major intersection. If the place is outside the study area, it should identify the other cordon station where the individual entered the study area. Any additional questions should be short, closed ended, and necessary for planning purposes. Trip purposes of frequency are examples. Other data gathered, but not asked should be the following: - The number of people in the vehicle - The vehicle type: - passenger car/light truck, passenger - light truck, commercial - heavy truck 6 Two products will evolve from the roadside interview when the data are tabulated: (1) the traffic volumes for the roadway segment at the cordon, and (2) a trip table for use with the system planning procedures. To obtain each, the following steps should be followed: STEP 1 - For each station location, summarize the interviews by vehicle type (and direction, if appropriate). STEP 2 - Divide the total count (by vehicle type) by the number of drivers interviewed to obtain the basic expansion factor. STEP 3 - Adjust the total counts for seasonal variation as previously described. STEP 4 - Code the geography of the trip origin and destination for each trip surveyed. These will be coded to an external station or to a traffic analysis area within the study area. STEP 5 - Multiply each survey by the expansion and adjustment factors to get the vehicle volume and vehicle trip table for the station. If origin and destination information is not required for travel across the cordon, the following simplified procedure based entirely on traffic counts may be used. STEP 1 - Draw the study area boundary on the map of roadway facilities. See System Planning manual, Chapter One. STEP 2 - Place a traffic counting station at each point where an arterial (including freeways) crosses the boundary. STEP 3 - Following the counting procedure previously described, inventory traffic at each of the locations. Locations where data are already being collected need not be tabulated again. For more detailed information, consult the section on external travel in the System Planning manual, Chapter Three and the Urban Origin- Destination Surveys, Chapter Six. 6/ 7 INVENTORY OF THE PUBLIC TRANSPORTATION SYSTEM An inventory of the public transportation system will include services, equipment used in revenue service and fixed facilities.7/ The inventory will consist of map files and tabulations. A checklist of requirements includes the following items: - Map of Transit Routes by Type of Service (e.g., express, local) - Map of Service Areas for Each Transit Operator (franchise, service areas) - Map of Actual Service Areas (areas actually served) - Tabulation of Schedules, Service Periods, Service Levels and Tariffs - Tabulation of Equipment Used for Regular Passenger Service (revenue equipment) - Tabulation of Potential Revenue Equipment (vehicles used locally to serve selected public markets such as the elderly programs) - Tabulation of Fixed Facilities (passenger, maintenance and admini strative) The transit routes for fixed-route service should be plotted on the same scale base map as the roadway system. Routes should be distinguishable and should be categorized by service type - express service, regular service and special service such as shopper specials. Using the base map and the route map, a series of overlays can be prepared which, in total, can describe the complete physical public transportation system. To determine the actual service area for fixed- route systems, a band 1/4 mile on either side of the route can be constructed. For demand responsive service, while a route is not apparent, the service areas will describe the service zones. These overlays will be useful later when compiling statistics for monitoring service.8/ Another overlay should describe the franchise service area. The franchise service area is the area in which the public transportation system has the legal authority to operate. All systems, whether public or private, will have a franchise service area. In towns and cities where the franchise area is restricted, 8 the existing system coverage can be evaluated and compared to the potential area of coverage. If the study area contains more than one public transportation systems each system should be tabulated and mapped separately, The systems considered should include taxicab operations and suppliers of special services in addition to the bus operators. A companion to the service maps should be a tabulation of all routes, Schedules and fare structures, by operating authority. If the operation is private, the public utilities commission or other regulatory body will have complete files. If the operation is public, the analyst should look to the operator for information. The analyst also should be aware of private operators who are leasing vans or list buses for ridesharing programs, which many communities have. All public vehicles used for passenger transportation in the study area should be included in the inventory. The word "public" includes services for special classes of passengers such as vocational rehabilitation program recipients. Vehicles should be inventoried to show the following data: - Company or agency owned/leased - Year of manufacture - Model and manufacturer - Seating capacity - Special equipment (e.g., wheelchair lifts) Fixed facilities should be inventoried. The amount of administrative and maintenance space available will indicate the capacity for expanding public transportation service. The inventory should not carry through to such items as bus stop signs and passenger waiting shelters. If and when this type of detail is needed, it can be inventoried. The study staff should produce only those data needed for the transportation planning process. INVENTORY OF LAND ACTIVITY Land activity information is a primary need in transportation planning. The trip generation element (see System Planning manual) provides the linkage between land activity and travel. Land activity information for trip generation is usually described in terms of land use intensity, character of the land use activities and location within the urban environment. Analysis Areas Prior to preparing a land activity inventory, a description of the analysis areas is needed for applying the transportation planning procedures. 'Guidelines for determining analysis areas are provided in the System Planning manual. Analysis areas provide the geographic units for which transportation information is developed. They are shown here in Table 1. 9 TABLE 1 NUMBER OF SUGGESTED ANALYSIS AREAS Urban Area Number of Population Analysis Areas 25,000 10- 15 50,000 20- 30 75,000 30- 50 100,000 35- 60 125,000 45- 75 150,000 55- 90 175,000 65-100 200,000 75-125 10 One of the most useful data sources to the transportation planner is the decennial census. The U.S, Bureau of the Census publishes its data by geographic area using both census tracts and enumeration districts. For a definition of tracts and enumeration districts refer to 1970 Census User's Guide.9/ Because census data are very useful, it is recommended that the transportation analysis areas selected by the transportation study group correspond to the census tract boundaries. The census tracts may be too large in many portions of the study area, so the analyst may want to subdivide them when defining the transportation analysis areas. However, care should be taken that the outer boundary of a group of analysis areas corresponds to the boundary of a census tract. It is also desirable for the analysis areas to represent a specific major type of land activity. For example, an area may represent a predominantly residential area, but other types of activity may also be present, such as a neighborhood shopping or office complex. The following steps are recommended for charting the analysis areas: STEP 1 - Using the base map, prepare an overlay showing the geographic areas used for the decennial census - census tracts and/or enumeration districts. STEP 2 - In general terms prepare a land activity map of the study area. Categories of land activity should be limited to; - Residential - Commercial - Industrial - Open Space This task can be accomplished by someone familiar with the study area and need not be a definitive inventory. STEP 3 - Overlay the roadway inventory onto the land activity map. It is desirable to subdivide analysis areas along major roadway facilities, particularly freeways. STEP 4 - Using the land activity map as a guide, subdivide or aggregate the census boundaries to form the Traffic Analysis areas. Table I will guide the formulation of the number of analysis areas. Once the boundaries are defined, the analyst is prepared to collect demographic data for the small areas. These analysis units will be used in the transportation planning process through the evaluation of future year scenarios. The following sections will describe land activity data in three forms: 1) type of land use 2) number of residents 3) number of employees 11 For the base year, the analyst can obtain each of the data categories with approximately the same level of effort, Future estimations of land use data will probably require less effort than population and employment data, Consequently, the analyst should be familiar with the trip generation provisions of the System Planning manual, since the areawide analytical procedures require residential and employment data, Land Use Data The System Planning manual provides tripmaking characteristics for a wide range of land use categories. The analyst will need to decide the degree of stratification desirable for the study area under investigation. However, the amount of data should be kept to a minimum. The land use categories required by the systems analysis procedures are, by design, limited to data sufficient to determine retail and non-retail employment for each analysis area. Data on dwelling units are also required. Land use data is probably available locally from secondary sources. The only new data that may be required can be found through personal observation of the analysis areas. For inventory purposes, existing land use data can be obtained from sources such as those show in Table 2.10/ Host urban areas have completed some form of land use study and are beyond the need of this inventory. In that event, the transportation planning study group should secure the plan for future use and organize the data by traffic analysis area. Population and Household Characteristics Population and household characteristics should be inventoried in tabular form, by traffic analysis area, for the base year. The tabulations should also be converted to a graphic presentation. These graphic presentations will aid the planner in analyzing the information. Secondary data available for the smaller urban areas preclude the need to collect original population-related data. Information should be obtainable locally. If not, it can be purchased from a commercial data firm such as R.L. Polk. The data required for transportation planning are not extensive, but the analyst may wish to augment the basic data with additional information on characteristics that can be used for other analyses. The basic data required to describe population and household characteristics include: - Dwelling units - Income distribution - Autos per household In addition to the basic data, other information is useful for comparing inventories to data which will be monitored in future years to assess changes. These data need not be compiled at the traffic analysis area level - it is sufficient if they are tabulated areawide.11/ Population composition by age group can be used to assess changes in household size and changes in transportation system needs. For example, significant increases in the elderly population 12 TABLE 2 SOURCES OF LAND USE DATA DATA SOURCE REMARKS Aerial Photography Secondary source, excellent for verifying other information. U.S. Census (decennial Primary source for housing; may & Special Census) require disaggregation to traffic analysis zones. Tax Assessor Primary source for all land use types. Planning and Zoning Agency Primary source for monitoring. can assist with inventory if historical files are maintained. Community Development Agency Primary source for recently redeveloped communities. Chamber of Commerce Secondary source, principally for commercial and industrial data. 13 may indicate a need for increased public transportation. Also, large numbers of youths and students may not have access to an automobile and may depend heavily upon public transportation.. For the base year, provided it corresponds to a decennial census or special five year census, dwelling unit data are available by census geography. In those areas with over 50,000 population, data are available at the block level and can be aggregated to the traffic analysis areas of the study area. Of course, population data are available from the same source and can be tabulated at the same time.9/ Household income data are also available from the census population reports. The inventory may preserve the income distribution shown in the System Planning manual's trip generation tables. In forecasting income the classifications may be reduced, especially if other trip generation tables are to be utilized. As with much of the data, the number of strata is dependent upon local needs. In urban areas with overall growth of less than two percent per year, data should be compressed as much as possible. A suggested income classification based on 1979 incomes is shown in Table 3. Income data maybe available from local sources such as the State revenue agency. The agency in each State has a file of personal income for tire preceding year that can be summarized by analysis area to yield the number of households within each income stratum. Since the files are generally confidential, procedures must be worked out with the State revenue office to ensure the protection of privacy. Obtaining income information in this manner should be carefully assessed to determine if it is cost-effective. Data on autos per household are available from the census tabulations. If census data are used for tabulating other household characteristics, the same source should also be used for auto ownership information. Auto ownership data may be obtained through State motor vehicle registration files. It is recommended that the transportation analyst develop a control total from autos registered, even if census data is used, for comparison. The auto registration files, like income data from the State revenue office, will require address coding to the appropriate traffic analysis zone and aggregation, by household, to get the range of households by auto ownership. Again, obtaining auto ownership data in this manner should be carefully assessed to determine if it is cost-effective. Employment Data Employment data are difficult to secure, For system planning purposes, it is only necessary to stratify employment into two groups: retail and non-retail employment. Even so, the inventory may require considerable effort if an employment file does not currently exist. Because of the effort, the analyst will want to consider converting land use data to employment by applying employee rates per acre or gross floor area (GFA). Such information is available from trip generation studies made for major trip generators by many States and metropolitan planning organizations. Table 4 14 TABLE 3 RECOMMENDED STRATIFICATIONS OF HOUSEHOLD INCOME STRATA HOUSEHOLD INCOME RANGE 1 $0 - 5,000 2 $5,000 - 7,999 3 $8,000 - 9,999 4 $10,000 - 14,999 5 $15,000 - 19,999 6 $20,000 - 24,999 7 $25,000 - 34,999 8 $35,000 - 49,999 9 $50,000 + 15 TABLE 4 EMPLOYEE RATES BY LAND USE TYPE GENERATOR EMPLOYEES PER 1000 sq. ft. GFA Acre RETAIL Free Standing Discount Store 0.9 Discount Store with Super Market 2.7 Department Store 1.1 27.4 Shopping Center Regional (over 1 million sq. ft.) 1.1 18.8 Community (100,000-500,000 sq. ft.) 1.7 18.1 INDUSTRIAL/MANUFACTURING Free Standing General manufacturing 1.8 17.6 Warehouse 1.2 15.3 Research/Development 2.1 25.3 Industrial Park 2.3 18.4 General Light Industry 1.7 16.4 All Industry Average 1.8 20.0 OFFICES General 3.3 21.4 Medical 2.5 17.0 Governmental 4.0 5.5 Engineering 6.6 80.6 Civic Center 4.1 5.4 Office Park 6.4 83.9 Research Center 3.0 11.9 PARKS AND RECREATION County Park 0.2 HOSPITALS All Categories 6.6 ___________________________ Source: National Cooperative Highway Research Program, Report 187: Quick Response Urban Travel Estimation Techniques and Transferable Parameters,User's Guide, (Washington, D.C., Transportation Research Board, 1978). 16 is an example from information in Quick Response Urban Travel Estimation Techniques and Transferable Parameters, User's Guide.12/ Retail employment is associated with commercial sales. It includes department stores, supermarkets, specialty shops, etc. Non-retail employment includes the following categories: - Government - Office - Financial, Insurance & Real Estate - Industrial - Manufacturing Other local sources the analyst may use to create an employment base file include the offices of employment security, the community or State planning office and the Chamber of Commerce. Also, the Bureau of the Census provides useful tabulations.9/ If the population and dwelling unit data were derived from census information, the analyst will want to verify employment rates between the sources in order to resolve discrepancies and avoid gaps in the employment data file. 17 CHAPTER TWO MONITORING Monitoring is an important planning function that should be considered as two activities. The first is gathering sufficient data to assess the trends of development and travel. The trends will show if the transportation system is performing as anticipated and will help identify potential problems. The second is keeping current the basic transportation information needed for system planning. The following major categories of information should be considered in monitoring: - Change in Land Use,Population, Dwelling Units and Auto Registration - Change in Employment - Change in Vehicle Miles of Travel - Change in Transit Patronage - Changes in Transportation System Service and Operation ESTABLISHING A MONITORING PROGRAM Monitoring should be considered as a continuing activity. The transportation study team should discuss individual participation and agree on a monitoring program. Liaison should be established with agencies which can supply information to the transportation study. A list of agencies which may contribute to the monitoring program are shown in Figure 2. Specific needs should be discussed with the State revenue office and other such agencies to secure their cooperation. The monitoring program should be formally established to inform each agency and individual about what is required of them and when. Monitoring activities will vary by urban area size and growth rate. Stable urban areas probably need to monitor activities only for the area as a whole. Monitoring by separate traffic analysis areas is worthwhile only when major changes occur or when the growth rate is greater than two percent per year. The following sections describe monitoring activities as they would occur in a fast growing urban area. Depending upon the characteristics of the urban area, the monitoring activities may not have to be detailed. Monitoring for System Performance Assessing the trend of general development and system performance should not take large quantities of staff time and effort. The monitoring process should be established as follows: STEP 1 - Collect data to assess changes in the major listed items above. STEP 2 - Compare changes to the trends forecasted. If trends appear as anticipated, do not continue through the following steps and continue monitoring at the study area level. 18 DATA TYPE ____________________________________________________ AGENCY LAND POPU-EMPLOY- DEMO- ROADWAY PUBLIC TRAVEL USE LATION MENT GRAPHICFACILI- TRANS- TIES PORTATION FEDERAL Bureau of Census X X X X US Department of Transportation X X STATE Dept. of Transportation X X State Planning Agency X X X X Revenue Office X Motor Vehicle Dept. X X Employment Security X LOCAL Planning and Zoning X X X X Traffic Dept. X X X Utility Dept.s X Building and Permits X X Chamber of Commerce X X X Public Transp. Agencies X X ___________________________ SOURCE: Worrall, R.D. & Robertson, S., Development of Information System for the Urban Transportation Planning Process, (Washington, DC, Transportation Research Board, 1973. FIGURE 2 POTENTIAL SOURCES OF DATA 19 STEP 3 - If the monitoring program indicates travel demand or development is not following the projected trends, stratify the basic data monitored to assess the geographic locations within the study area which are deviating from projected trends. STEP 4 - Determine if the deviations are in confined areas or impact the entire study area. If the problem is local, assess the impact on the transportation system. If necessary, modify the development forecasts and the forecast year plan, If problems exist areawide, the analyst should evaluate the forecasts and the transportation improvement program, Either modify the long-range estimates or the policy on growth. STEP 5 - If unexpected changes are occurring to the transportation system for example, if vehicle miles of travel is increasing rapidly or if transit patronage is rapidly declining - the reason should be sought out and appropriate action taken. As with development changes, forecasting procedures may require modification or the transportation program may need to be modified. STEP 6 - In the event of major problems, Steps 3-5 should be followed until the transportation planning process is in harmony with growth trends. Monitoring to Update Inventory Information Some of the inventory information will be updated when monitoring for evaluating system performance as described in the previous section. Files on roadway volumes, for example, can be kept current when collecting data using hose counts to estimate vehicle miles travelled (VMT). Any file requiring traffic analysis area data should not be updated as specified by the normal monitoring schedule shown in the next section. Except in areas anticipating fast growth (greater than five percent per year), the files should be updated concurrent with the decennial census. The primary purpose of these files is to supply input to the system planning procedures. All information should be identified as to source and agency responsibility. Data such as changes in land use will generally be on file with the local office of planning and zoning, and can easily be shared with the transportation study staff. Supported by certificates of occupancy issued to new developments, the data sources will be prepared to respond to an update at a small geographic analysis area level. Scheduling of Data Items to be Monitored Monitoring the primary data items should be scheduled as part of the overall transportation planning process. A suggested schedule for monitoring in areas experiencing moderate growth, between about two and three percent per year, is shown in Table 5. All socioeconomic data are intended to reflect areawide chances which occur during the monitoring period. Under the normal surveillance program, locating the changes within the study area is not required. The absolute change 20 TABLE 5 SUGGESTED MONITORING SCHEDULE for Communities Experiencing Moderate Growth MONITORING INTERVAL DATA ITEM (Years) LEVEL OF DETAIL Socio-Economic Population 2 Areawide Dwelling Units 2 Areawide Employment (Total) 2 Areawide Auto Registrations 2 Areawide Land Use 2 Areawide by category Transportation System Roadway Mileage 2 Functional Classification Vehicle Miles of Travel 2 Functional Classification Transit Revenue Vehicle Miles 2 Areawide Transit Revenue Passengers 2 Areawide Transit Total Passengers 2 Areawide Transit Service Area (1-4 Mile Bandwidth) 4 Areawide Transit Vehicle Age Distribution 2 Areawide ___________________________ Source: U.S. Department of Transportation, Data for Urban Transportation Planning, (Washington, D.C., 1978) 21 in population or dwelling units, auto registrations and employment can be compared to the expected growth rate between the base year and forecast year to determine if the actual growth is following the anticipated growth trends. Land use should be tabulated using the categories currently in use within the small urban area. The following categories will provide sufficient detail: - Residential - Commercial - Industrial - Open Space - Other (i.e., streets, power substations, etc.) Roadway mileage should be tabulated by functional classification as described in Chapter One. The monitoring of system change should be consistent with the inventory. Changes in roadway mileage do not serve as an indicator of system performance. However, coupled with changes in vehicle miles of travel by functional classification, the use of each roadway type can be monitored. Monitoring the transit data listed in Table 5 is recommended, based on the Urban Mass Transportation Administrations Uniform System of Accounts and Records.13/ The system is structured around fixed-route transit service but can be adapted to demand-responsive service as well. For demand-responsive service, the 1-4 mile service area should be defined as the total service area of the system. Transit vehicle data should be collected for the following age groups: - Under 5 years old - 5-9 years old - 10-14 years old - 15-19 years old - 19+ years old Vehicle data will be useful for monitoring average fleet age and transit vehicle replacements. System operations obtained through discussions with various individuals should not be overlooked when evaluating the transportation system performance. They include discussions with the traffic engineer, law enforcement agencies and the citizenry. Through their daily personal involvement, they can provide useful information for maintaining a viable transportation system. MONITORING TRAVEL DATA Two categories of travel data will be discussed here - roadway travel and public transportation travel. Techniques are presented for estimating the magnitude of travel for each. Travel data provides the key indicator of system performance and is of great assistance for operational planning in addition to system planning. Many urban areas collect traffic volume data, or a State or county agency might collect the data. The existing sources should be sought out prior to collecting new data in order to coordinate the programs. 22 Roadway Data Roadway use is, usually measured by vehicle counting through the use of automatic traffic counters. The procedure was. discussed in Chapter One. Also, as discussed in Chapter one, roadside interviews along major arterials and freeways define travel associated with trip origins and/or destinations outside the study Area. In addition to a traffic counting program it is also desirable to monitor auto occupancy. Changes in auto occupancy rates can significantly influence the amount of vehicle miles of travel in an urban area. Historically, the auto occupancy rate has remained fairly stable. Because of the promotion of ridesharing programs and growing concerns over energy consumption, more significant changes in the auto occupancy rates is likely. Estimating VMT from counts and roadway segment mileage is done by the State and can be extended to include the transportation planning study area. A variation of this technique involves application of sampling procedures for estimating VMT. Details of the sampling procedure are included in the Guide to Urban Traffic Volume Counting. 1/ With VMT being highly dependent upon auto occupancy, it is recommended that the average auto occupancy for the study area be reevaluated regularly when reporting VMT. In areas of moderate growth, every two years will be adequate. The procedure for monitoring auto occupancy is not complicated. It requires, in addition to automatic traffic counters at designated locations, personnel equipped with hand counters to classify the vehicles passing the location according to the number of people in the vehicle. The counter should be a standard classification traffic counter with six or more meters to tabulate the number of vehicles with from one to six or more occupants. For further detail on obtaining auto occupancy information, consult the Guide to Estimating Urban Vehicle Classification and Occupancy. 14/ Public Transportation Data Data collection for public transportation systems is required for proper operational planning as well as for monitoring the total transportation system. Changes in ridership demand and travel patterns must be responded to promptly in order for public transportation systems to capture new markets and continue to serve their existing clientele more expeditiously. Three procedures can be employed for monitoring transit ridership in the urban areas. They are: - Onboard origin-destination surveys - Load point checks - Ride checks 23 The onboard origin-destination survey, presented in detail in the Transit Planning manual, provides considerably more information than the latter two techniques but is also more costly. In the small urban areas where public transportation coverage is not extensive, the utility of the onboard survey is limited. Passenger load checks are designed to collect data economically for fixed-route transit service and can collect information about more than one route at the same time - depending on location. Locations along the transit route are generally selected for proximity to the maximum load point of the route. Figure 3 shows a typical form for use in load point checking. The data provide information on the schedule adherence of vehicles, passenger loads as compared to seats available and boarding/alighting activity at that particular location. Load point checking should be a regular activity at or near the maximum load points of transit routes. Each major load point should be checked monthly in the smaller urban areas. Checks should be for two consecutive days over a six hour period. The six hour period may begin at 6:00 a.m., or with the first a.m. trip past the check point. It may also end at 6:00 p.m., or the last p.m. trip past the check point, where the afternoon and p.m. peak periods are under investigation. The six hour period will cover the peak and base operations. Using consecutive day checks will allow the analyst to resolve variations peculiar to a specific day of operation. Checking should be done for typical operating days (normally Tuesday through Thursday) and, except for special operational studies, holidays should be avoided. Load point data are affected by the weather. Inclement weather causes abnormal fluctuations in ridership and should be avoided even if it requires last minute manpower scheduling changes. The data gathered are of importance to the operator as well as the local planner for evaluating system performance. Ride checks require an individual to ride a transit vehicle and monitor the number of passengers boarding and alighting at each bus stop. Ride checks can be used to profile the ridership along a fixed route or they can be used to profile trip activity of a demand- responsive system. For demand-responsive activities, the ride check does not require an individual to ride the vehicle, since a central dispatcher is controlling the stops. The dispatcher's log provides the same information as a ride check provides on a fixed route. Figure 4 is a typical form layout for ride checks. Comparison with the load point checking form reveals the following major differences: - A separate form is necessary for each vehicle. - Data are compiled on the form for each stop along the route. Each bus line or demand-responsive service area should be surveyed quarterly for operational planning, although such frequent monitoring is not required for general system monitoring. 24 Click HERE for graphic. FIGURE 3 TYPICAL LOAD POINT CHECK FORM 25 Ten percent of the vehicle trips should be included in the survey. The trips surveyed should reflect operations over the full operating day. Data from fixed-route service can be used to develop a ridership profile for the bus line or, where multiple bus lines operate over the same street, for the street. Data from demand-responsive service can be used to develop a transit trip matrix and develop a mapping of major travel desires via public transportation. Sample data collected from ride and load point checks can be combined with farebox revenue records to assess changes in the system. Comparing the farebox revenue to ridership on a day when checks are made allows for the development of a revenue/ridership relationship. As revenue is monitored, fluctuations in revenue can be interpreted to describe fluctuations in demand. Fare policy changes will also be evident in the revenue analysis. If fares chance or the mix of ridership changes--more senior citizens riding the system at reduced fares, for example--the revenue analysis will require adjusting. A reinventory of the revenue vehicle fleet related to public transportation service will normally be conducted annually, although for most small urban areas it is only required every two years. Changes in major capital investments are slow to occur; therefore, the data update should be relatively simple. Vehicle age, mechanical status and availability should be verified with the operators providing public transportation service within the study area. With the above travel data and a regular monitoring of revenue, the monitoring program will satisfy the information requirements for operational planning and, therefore, the data reporting requirements of the transportation planning study. MONITORING CHANGES IN LAND ACTIVITY Changes in land use will account for the major changes in employment and population of an urban area. Monitoring these changes will provide the transportation planning staff with details necessary to assess growth trends. Two data sources are recommended for monitoring land use changes. The first source is the submittals required by the city or county planning and zoning agencies for construction and other business purposes. This provides a tabulation of anticipated change and, therefore, can be used to forecast change for approximately a five year period. The second source is either certificates of occupancy or electric meter installations. These data will show actual changes in land use. The transportation planning study staff should receive major development submittals from the planning and zoning agency together with as much of the detail development plan as practical. Residential developments will be defined as to structure type and density in terms of units per acre. Commercial developments will specify the use type and gross floor area. Traffic impact statements are usually required with the development plan and will include estimates such as Population, employment, and travel demand. 26 Click HERE for graphic. FIGURE 4 TYPICAL TRANSIT RIDE CHECK FORM 27 Development plans should be mapped as, an overlay to the existing land use inventory to note changes, Comparisons should be made to determine if the actual plans are in conformance with the forecast estimates. Since the same procedure should be used for forecasting land use., a significant variance would not be expected for some years after the initial plan preparation year. After construction and prior to opening, each new structure is generally issued, by law, a certificate of occupancy signifying it has satisfied all building requirements. Tabulating the certificates of occupancy by land use type will provide an up-to-date file of residential, commercial and industrial development. For large commercial and industrial developments, the planning staff should contact the owner/occupant to inquire about the number of employees expected. If certificates of occupancy are not available, the new development can be monitored through the electric utility company when it installs a new electric meter. Large employers should be interviewed by telephone to determine the employment level anticipated. When updating land use files and maps to a current year, the analyst should remember to make appropriate changes to the land use categories which the new development replaces. Generally, this will represent a modification to the open space or vacant land files. To estimate the population served by public transportation for the current monitoring year, the analyst must convert dwelling unit changes into population. Dwelling units accumulated by traffic analysis area can be converted to population using the rate for other residential developments in the analysis area, or, if it is the only residential development in the analysis area, the areawide rate as determined from the census data or base year data files. 28 CHAPTER THREE FORECASTING The primary purpose of forecasting is to provide information for transportation system planning. It is recommended that forecasts be limited to the data items required for system planning. The specific variables needed are based upon the procedures described in the System Planning manual. The data items are as follows: - Population and Dwelling Units - Mean Income - Auto Ownership - Retail Employment - Non-Retail Employment The actual data sources used in each urban area will depend on data availability and the current level of effort in the urban area devoted to planning. The approach here is to provide direction for finding data that can assist the transportation analyst, assuming that forecast data is not available for small geographic areas. The user should consult the 1970 Census User's Guide 9/ to identify specific variables for measuring residential and employment activities. In addition, the Obers Projections 15/, will provide aggregate forecasts of the appropriate data. These references will also be helpful in preparing forecasts of auto ownership and income distribution. POPULATION AND DWELLING UNIT DATA To forecast population, first review the existing land use plan to determine the growth potential of the study area. This review must be balanced against development requirements for employment sites to maintain a balance in the labor participation rates. 15/ Second, the historical growth trends should be plotted to develop a realistic picture of the probable growth of the urban area. 16/ Unless the community has a policy for encouraging major growth, it is unlikely that the rate of growth will change drastically. The historical rate of change of persons per dwelling unit should be plotted to determine trends in household size, since dwelling units will probably be selected for estimation at the traffic analysis area level. The trend will provide insights for obtaining totals at the areawide level. The analyst will also wish to review the growth proposed for the study area as it relates to the growth of the State as a whole. The State planning agency will have forecast information and their data may be useful for establishing a total for the study area. 29 National projections of population and employment are prepared for the United States Departments of Commerce and Agriculture using the Bureau of Economic Analysis (BEA) geography. 15/ This source subdivides the United States into 173 economic analysis areas. Forecasts are made for each area based on distribution of national growth. The data can be used to develop totals for the study area based on growth rate and base year population. The information provided includes, through the year 2020: - Population - Per Capita Income - Total Employment The following procedure can be used to estimate population and dwelling units for each traffic analysis area: STEP 1 - Determine the areawide population control total from local sources or those mentioned above. STEP 2 - Determine the areawide dwelling unit control total using the population control total and the analysis of household size. STEP 3 - With the base year dwelling unit inventory and the proposed residential development proposals (converted to dwelling units), prepare the first estimate of projected dwelling units in the traffic analysis area and areawide. STEP 4 - The first estimate will not agree with the control total established in Step 2. An evaluation of the distribution should be made with the transportation study participants. The majority of participants should agree upon which traffic analysis areas should be modified and the magnitude of each modification. STEP 5 - Perform the modifications to determine a second estimate of dwelling units at the traffic analysis area level. STEP 6 - Factor the second estimate by the ratio of the areawide control (Step 2) to the areawide total from the second estimate to produce the dwelling units per traffic analysis area. These are the numbers to be used in forecast scenarios. STEP 7 - Reapply the analysis area factors found in Step 6 to convert population to dwelling units and the population estimates by traffic analysis area will be available. MEAN HOUSEHOLD INCOME Two phases can be used for estimating the mean household income for each traffic analysis area and preparing the estimates for input to the trip generation procedures. In phase I the forecast year mean household income is estimated for the 30 analysis area. In phase II the average is refined to determine the percent of dwelling units estimated to be in each income stratum. Phase I - Mean Income Estimation Mean household income for traffic analysis areas should be part of the inventory described in Chapter One. A basic source for such data would be the decennial census. Using information that may be available through the State, data developed on a county level, or Obers Projections, the income can be updated to a forecast year. Dollar values should be adjusted to the base data year using the consumer price index as described in the System Planning manual. The new residential developments identified as the "second estimate" (Step 5 of the previous section) should be analyzed to determine the estimated average income each will contribute in the traffic analysis area. Average income may be estimated by looking at other housing in the same analysis area or looking at another analysis area which has comparable housing to see if the new development is comparable. If the new development is comparable to the existing housing, an income adjustment is not necessary. If the average income for the new develop- ment is expected to differ from the current average income of the area, the analysis should reflect the difference. A weighted average should be developed based on the number of existing dwelling units multiplied by the existing average income and the number of new dwelling units times their established average income. The resulting average will represent an update of the base year income averages. The increase in per capita income can be applied to the updated base year traffic analysis area average income values to obtain future average income by small analysis area. The analyst may use the revised income values to apply the trip generation procedures described in the System Planning manual. Phase II - Distribution of Households by Income The income data for the analysis area can be refined to estimate the number of households in each income stratum. Several urban areas have been analyzed for household distribution by average income distribution. Definite relationships have been found to exist. 17/ Figure 5 shows the type of relationship that can be expected by making graphs from decennial census data. Once the revised average income for the forecast year has been determined, the analyst can enter a graph and determine the percent of households that can be expected in each income stratum. This procedure assumes that the income distribution of households remains constant over time. AUTO OWNERSHIP Auto ownership per household is an important trip related variable. Although not always required for trip generation (see System Planning manual), the analyst should forecast auto ownership to develop an areawide total. 31 Click HERE for graphic. FIGURE 5 DISTRIBUTION OF HOUSEHOLDS BASED IN AVERAGE INCOME PER ZONE 32 Auto registration by year may be obtained from the motor vehicle administration in the State summarized by city, town or county, In States where an ad valorum tax is assessed on cars, registrations are available from the tax assessor.-A plot of auto ownership within the study area superimposed upon the number of dwelling units of the area will show the trend of auto ownership per--dwelling unit. Interpolated values from the dwelling unit curves can be used with the auto registration to get the annual ratio and allow determination of a rate of change. The autos per household curve can be extrapolated to the forecast year by extending past trends. A forecast year rate can be determined. Applying the rate to the number of dwelling units anticipated in the forecast year will yield a forecast year control total for autos within the region. When applying the trip generation rates based on average household income, the tables provide an estimate of autos per dwelling unit for that income stratum. Multiplying the auto rate times the number of dwelling units will yield the number of autos in each traffic analysis area. To use auto ownership at the traffic analysis area level, the analyst should factor the estimates derived from the trip generation procedures so the areawide sum of autos is equal to the control totals developed from local auto ownership trends. EMPLOYMENT Forecasting employment follows the same general procedure as forecasting population. The same cautions are in order for arriving at control totals to ensure they are in keeping with other planning at the State level. Also, the labor participation rate (employment/population) should be reviewed to see if it follows past trends in the study area. Obers Projections 15/ provides past estimates as well as forecasts of employment to the year 2020. This is provided for a number of industry classifications. Using these data, employment can be forecast to develop areawide control totals and estimates at the traffic analysis area level. The only significant difference between forecasting population and employment is the requirement that employment forecasts should be classified into retail and non-retail employment (see System Planning manual). The steps required to develop forecast data for either employment category are: STEP 1 - Locate the major commercial developments anticipated between the base year and the forecast year by traffic analysis area. STEP 2 - Using employee rates per acre or per gross floor area, convert the development plans to employees and add the employment to the base year totals. The areawide sum is the result of a first estimate of either retail or non-retail employment. 33 STEP 3 - Compare the results from Step 2 with the areawide control total and adjust as required through a subjective evaluation, STEP 4 - Modify the first estimate to arrive at a second estimate of employment. STEP 5 - Adjust the employees per traffic analysis area uniformly so that the sum of employment is equal to the regionwide control total. The results of Step 5 will be the employment forecasts that will be used. in the trip generation procedures described in the System Planning manual. 34 REFERENCES 1. U.S. Department of Transportation, Federal Highway Administration, Guide to Urban Traffic Counting Manual, (Washington, D.C., 1980). 2. National Committee on Urban Transportation, Procedure Manual 3A Measuring Traffic Volumes, (Chicago, Public Administration Service, 1958). 3. Smith, W., Transportation & Policy for Tomorrow's Cities, (New Haven, 1966). 4. National Committee on Urban Transportation, Procedure Manual 2A Origin-Destination and Land Use, (Chicago, Public Administration Service, 1958). 5. Brant, A.E. & Low, D.D., "Cost Saving Techniques for Collection and Analysis of Origin-Destination Survey Data," Highway Research Record No. 205, (Washington, Transportation Research Board, 1967). 6. U.S. Department of Transportation, Federal Highway Administration, Urban Origin-Destination Surveys, Dwelling Unit Survey, Truck and Taxi Surveys, External Survey,_(Washington, D.C.). 7. U.S. Department of Transportation, Urban Mass Transportation Administration, External Operative Manual, (Washington, D.C., 1972, amended). 8. U.S. Department of Transportation, Federal Highway Administration, Data for Urban Transportation Planning, (Washington, D.C., 1978). 9. U.S. Department of Commerce, Bureau of the Census, 1970 Census Users' Guide, (Washington, D.C., 1970). 10. Worrall, R.D. & Robertson, S., Development of Information System for the Urban Transportation Planning Process, (Washington, D.C., Transportation Research Board, 1973). 11. Lagomarisino, L.C., & Matthias, J.S., Determining the Need for Updated Transportation Studies in Smaller Urban Areas, (Washington, D.C., Transportation Research Board, 1977). 12. National Cooperative Highway Research Program, Report 18, Quick Response Urban Travel Estimation Techniques and Transferable Parameters, Users' Guide, (Washington, D.C., Transportation Research Board, 1978). 13. U.S. Department of Transportation, Urban Mass Transportation Administration Uniform System of Accounts Records - Implementation, (Washington, D.C., 1977). 14. U.S. Department of Transportation, Federal Highway Administration, Guide to Estimating Urban Vehicle Classification and Occupancy, T-Washington, D.C.). 35 15. U.S. Water Resources Council, Obers Projection, Volume 2, (Washington, D.C., 1974). 16. U.S. Department of Commerce, Bureau of the Census, Guide for Local Area Population Projections, (Washington, D.C., 1977). 17. U.S. Department of Transportation, Federal Highway Administration, Trip Generation Analysis, (Washington, D.C., 1975). U.S. GOVERNMENT PRINTING OFFICE : 1980 0-320-194/6268 36