4.0 Operational Objectives for Transit Data in an ICMS
The overall operational objective for an ICMS is to keep all of the component networks operating optimally all the time. The ICMS allows for the integration of transportation-related data across the corridor. Each agency within the network will have the necessary data and/or control to assist in facilitating the optimal movement of people and goods through the corridor. To manage a corridor in an integrated fashion requires the corridor manager to develop and implement strategies in four areas:
- Demand management
- Load balancing
- Event response
- Capital improvement
These strategies must be supported by the ICMS within the time constraints of the decisions that must be made. The ICMS corridor has three major time horizons for operation. These time horizons are:
- Current (a.k.a. ‘real-time’)
- Planned Event (including pre-planning for emergencies and disasters)
- Long-term Planning and Optimization
These time horizons correspond to two distinct operating modes for corridors: Normal mode and Event mode. Normal mode is the mode that constitutes all the actions it takes to ensure that day-to-day transportation needs are addressed. Event mode has two sub-modes: Planned Event mode and Unplanned Event mode.
Planned Event mode is the mode where, prior to its occurrence, it is known that an event affecting corridor capacity or travel demand will occur. Capacity may be reduced due to construction, anticipated weather conditions, or a special activity such as a parade. Travel demand may increase due to a large venue activity like a sporting event.
Unplanned Event mode is the mode where an event changes corridor capacity or demand with little or no prior warning. This could be a current event (an incident that reduces capacity) or an emergency situation corresponding to one or more emergency/disaster plans (e.g., an evacuation).
A corridor may shift between Normal mode and Event mode several times during a single day, or even shift from one Event mode to another. In some cases (e.g., during construction or long-term maintenance activities), a Planned Event mode may become the “normal” operation mode.
A corridor does not change modes automatically. Whatever the triggering event, the corridor manager has to assess the severity and impact on the entire corridor, and expected duration of an event before deciding the operational response. If the severity of an event is low, there may be no need to change operational modes or adopt a new operational strategy.
4.1 Current Time Horizon
The current time horizon is the real-time activity within the corridor. Whether the corridor is in Normal mode or Planned Event mode makes little difference to the corridor operators. The transportation network operators respond to changing conditions by evaluating the surveillance and detection data, sharing event information, and implementing controls to mitigate the impact of the unplanned events on all parts of the corridor. The overall scale of the unplanned event will affect the data needed to meet the operational objectives and large incidents may require more data sharing and coordination than smaller incidents. However, the defining characteristic of the current time horizon remains the same: responses are constrained by the resources at hand and the current capacities of the corridor transportation systems.
Transportation network operators and/or decision support systems may be able to recognize similarity between the impacts of different incidents. Using experience and historical data, in addition to current data, they may be able to take a pre-planned response for another event and use it as a basis for the response to an incident.
Typically, in this operational horizon, transit agency operators can respond to unplanned events by making appropriate route changes in order to maintain transit schedules. Depending on the nature, timing, and expected duration of the unplanned event, transit agency operators may be able to coordinate with transportation managers and direct drivers to change modes. In order to affect a mode change, drivers would need to know parking and transit availability. It has been noted that drivers may be more open to mode shift on the initial portion of their trip (i.e., drivers are more likely to shift to transit during the AM peak than the PM peak). This is possibly due to the concern of how and when the driver can get back to where his or her car is parked.
Transit managers have indicated that real-time capacity data may not add significant value to the transit operation. Several reasons were given for this view.
- First, most transit vehicles are equipped with radio and/or mobile data terminals through which an operator could report a “full vehicle.” In some places, parking lot attendants make similar reports by radio when lines at their stop become substantial. Transit management would be able to determine if an additional vehicle and driver were available to add to the route.
- Second, many transit agencies have limited spare vehicles and drivers.
- Finally, the amount of time needed to get an additional vehicle to a specific route may be too long to have an effective impact.
Although the lack of additional operators (or drivers) applies to both rail and bus systems, rail systems can often add spare rail cars to current trains to form consists without adding operators (though Federal Railroad Administration rules and union contracts can impose limits on adding cars). This brings into play an additional limitation: rail consists can only be as long as the shortest platforms on the run and cars can only be added at yard locations where the cars are stored. Even with these limitations, rail transit has a significant advantage for meeting increased demand. An additional operator is not necessarily required for more capacity, and rail cars typically have more capacity than a bus.
4.2 Planned Event Time Horizon
The planned event time horizon involves an event within the corridor for which there was prior notification and time to plan the corridor optimization for the event. Pre-planning the response to an event allows the transportation network planners the opportunity to model different responses.
Modeling algorithms will use historical data to validate solutions. This type of modeling may be done with traditional corridor modeling tools or with decision support modeling. The pre-planning exercise allows different agencies within the corridor to work together to optimize the response. In a planned event mode, the ICMS should be capable of evaluating multiple strategies and identifying the likely impacts of each strategy with regard to the performance measures and capacity utilization on all transportation modes within the corridor. If this planning does not identify a strategy that will avoid capacity overloading of one or more of the corridor transportation assets, the corridor participants must understand, in advance, the likely impacts of the selected plan.
- During the planning, it may be determined that additional capacity within the affected area is needed and some routes may be designated as one-way for the duration of the event.
- Transit agencies may respond by providing more high occupancy vehicles and lower cost parking and shuttles to and from satellite parking locations.
- In order to add additional capacity, transit agencies may need to schedule and pay overtime to transit vehicle operators.
- Public safety agencies and road maintenance agencies may need to assist during the event with the reconfiguration of roadways.
4.3 Long-Term Planning and Construction
This time horizon allows the agencies within the corridor to review the current corridor optimization and then determine if there are additional intersections, lanes, transit vehicles, or other ICMS infrastructure needed. Current usage is reviewed and historical data is used to model new configurations. Each configuration is optimized to determine the impact of the proposed modifications and determine which modification has the highest benefit/cost ratio. Long-term planning and construction allows for the building of new roadways, implementation of high occupancy vehicle incentives, and addition of mass transit options.
Long-term planning is usually thought of in terms of capacity planning. To the extent that current and short-term operational decisions are made on the basis of optimizing capacity utilization, long-term planning is an extension of ICM strategies.
4.4 Summary
Demand management, load balancing, event response, and capital improvement are all ways of getting the most “bang for the dollar” out of existing and future investments in corridor transportation capacity. Regardless of how the public measures satisfaction with transportation, transportation providers are investing based on demand for capacity and cost per incremental change in capacity. It is imperative then, that good corridor management depend on measures of capacity utilization, cost of capacity, and the optimization of existing capacity to meet current needs.
