Transportation Management Plan Effectiveness Framework and Pilot
Executive Summary
A Transportation Management Plan (TMP) lays out a set of coordinated transportation management strategies and describes how they will be used to manage the work zone impacts of a road project. The scope, content, and level of detail of a TMP may vary based on the State or local transportation agency’s work zone policy, and the anticipated work zone impacts of the project. In some cases, a regional TMP may be developed to better mitigate the combined effects of several projects occurring within a corridor or roadway network.
Ideally, a practitioner developing a TMP would choose those TMP strategies that provide the best benefit-to-cost effect in terms of mitigating work zone impacts. Unfortunately, information on the actual effectiveness of many of the TMP strategy is lacking. TMP strategies attempt to mitigate impacts by:
- Increasing the amount of traffic-carrying capacity through the work zone or on alternative routes.
- Performing work that reduces capacity when traffic volumes are lower.
- Encouraging additional travel diversion away from the work zone beyond what would have happened otherwise.
- Reducing traveler surprise to unexpected conditions and features.
- Encouraging safer driving behavior through the work zone.
- Reducing the consequences of an errant vehicle leaving the travel lane relative to what would have happened if the mitigation strategy had not been employed.
- Reducing the consequences of crashes that do occur.
- Reducing other worker accident risks by providing more work space in which to operate.
- Reducing the duration of the work zone.
- Reducing public frustration and anxiety about the work zone.
Consequently, different measures-of-effectiveness (MOEs) are needed to evaluate the effectiveness of different strategies. In general, TMP strategies can be evaluated through one or more of the following MOE dimensions:
- Mobility.
- Safety.
- Customer satisfaction.
- Agency and contractor productivity and efficiency.
Many strategies affect MOEs in more than one of these dimensions, regardless of whether they are implemented specifically to mitigate work zone impacts within that dimension. Consequently, the effectiveness of multiple TMP strategies implemented at a work zone will often confound each other to generate an overall effect on impacts at that location. In some cases, methods do exist to dissect the influence of individual TMP strategies, but these typically require data from multiple projects and more advanced analytical techniques.
Multiple ways exist to assess whether a TMP strategy had some type of effect on one or more measures used to assess work zone safety and mobility impacts, specifically:
- Qualitative assessments.
- Quantitative assessments.
- Some hybrid of the two.
Meanwhile, assessments of TMP strategy effectiveness can also vary in scope. Common evaluation scopes include:
- Full-scale evaluation of all strategies on a project.
- Agency-wide evaluation of a single TMP strategy.
- Research evaluation of a single strategy implemented by several agencies.
- Case study of a single strategy at one location.
- Process review.
Ultimately, the selection of MOEs to use, assessment approach, and assessment scope varies depending on the question the practitioner is trying to answer, such as:
- Do we think this TMP strategy (or set of TMP strategies together) had some type of effect upon mobility, safety, customer satisfaction, and/or agency or contractor productivity and efficiency? In simplest terms, do we think this strategy was "effective?"
- How much of an effect did this TMP strategy/set of strategies have upon mobility, safety, customer satisfaction, and/or agency or contractor productivity and efficiency MOEs?
- How does the effectiveness of this TMP strategy/set of strategies upon mobility, safety, customer satisfaction, and/or agency or contractor productivity and efficiency vary as a function of differences in roadway, traffic, and work zone characteristics?
The challenges posed in assessing the effectiveness of TMP strategies to mitigate work zone impacts are particularly noteworthy. If introducing a work zone on a route adversely affects operating conditions on the route to a significant degree, a certain percentage of drivers will choose to alter their trip-making behavior by departing at a different time, changing their route, or perhaps even changing their choice of travel mode. This will occur even if no TMP strategies to encourage those changes are implemented. Conversely, the number of travelers modifying their trip-making behavior will affect how significantly the work zone itself affects operating conditions on that route. This same type of circular relationship between changes in trip-making decisions and the resulting operating conditions will also exist on alternative routes in the corridor. Therefore, strategies that attempt to also affect trip-making decisions and behaviors need to be measured not against what was happening before the work zone was introduced into the corridor, but rather measured relative to what would have occurred had the strategy not been implemented.
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