5.0 Performance Measures
This section details the performance measures to be used in the evaluation of ICM strategies for the Test Corridor. To be able to compare different investments within a corridor, a consistent set of performance measures will be applied. These performance measures:
- Provide an understanding of existing traffic conditions in the study area;
- Demonstrate the ability of ICM strategies to improve corridor mobility, throughput, reliability, and safety based on current and future conditions; and
- Help prioritize individual investments or investment packages within the Test Corridor for short- and long-term implementation.
To the extent possible, the measures will be reported by:
- Mode – SOV, HOV, transit, freight, etc.;
- Facility Type – Freeway, expressway, arterial, local streets, etc.; and
- Jurisdiction – Region, county, city, neighborhood, and corridor-wide.
The performance measures focus on the following three key areas. Additional information on these measures is provided in the “ICM AMS Methodology” document.
- Mobility – Describes how well the corridor moves people and freight;
- Reliability – Captures the relative predictability of the public’s travel time; and
- Safety – Captures the safety characteristics in the corridor, including crashes (fatality, injury, and property damage).
5.1 Mobility
Mobility describes how well the corridor moves people and freight. The mobility performance measures are readily forecast. Two primary types of measures will be used to quantify mobility in the Test Corridor, including the following:
- Travel time – This is defined as the average travel time for the entire length of the corridor or segment within a study corridor by facility type (e.g., mainline, HOV, and local street) and by direction of travel. Travel times will be computed for the peak period.
- Delay – This is defined as the total observed travel time less the travel time under uncongested conditions, and will be reported both in terms of vehicle-hours and person-hours of delay. Delays will be calculated for freeway mainline and HOV facilities, transit, and surface streets.
5.2 Reliability of Travel Time
Reliability captures the relative predictability of the public’s travel time. Unlike mobility, which measures how many people are moving at what rate, the reliability measure focuses on how much mobility varies from day to day. For the Test Corridor, travel-time reliability will be calculated using the simulation models by performing multiple model runs for all scenarios.
A combination of the “Buffer Index” and the standard deviation of travel time for the peak period will be used to report travel-time reliability for the Test Corridor. The buffer index is defined as the extra time (or time cushion) that travelers must add to their average travel time when planning trips to ensure on-time arrival. On-time arrival assumes the 95th percentile of travel-time distribution. The buffer index is the difference between the 95th percentile travel time and the average travel time for the peak period divided by the average travel time:
5.3 Safety
For the safety performance measure, the number of accidents and accident rates from accident databases will be used for the Test Corridor. For the Test Corridor, safety analysis will be conducted qualitatively using expected levels of improvement in safety as a result of deploying mitigation strategies (e.g., major improvement, minor improvement, none, slightly worse, etc.).
5.4 Cost Estimation
For the identified mitigation strategies, the analysis team will prepare planning-level cost estimates, including life-cycle costs (capital, operating, and maintenance costs). Costs will be expressed in terms of the net present value of various components.