Abstract
Highway congestion is still a major problem in traffic operations and management, and the search for feasible mitigation measures continues to evolve with advancement in technology and better understanding of traveler behavior. Many congestion mitigation strategies have been implemented in the past; but they were unable to improve traffic conditions for entire transportation corridors due to lack of coordination among corridor stakeholders. These strategies were implemented on individual transportation facilities in a corridor and often ended up improving conditions on one facility at the expense of others. Therefore, coordinating the management of transportation facilities within a corridor offer an opportunity to operate and improve traffic conditions in the entire system as opposed to individual facilities. This concept of congestion management is referred to as Integrated Corridor Management (ICM).
While ICM holds the potential to mitigate highway congestion, a major problem faced by transportation agencies who intend to adopt its use is the identification and selection of the most beneficial strategies to implement in a corridor. This research proposed a five-step ICM evaluation methodology based on which strategies that will benefit the operational needs of a transportation corridor can be identified. The proposed evaluation methodology was applied to a real-world transportation corridor in northern Virginia (section of I-95/I-395) to determine the feasibility of ICM implementation in this corridor using a simulation. Based on the analysis of simulation results, variable speed limit system, increasing transit and parking capacity, HOV lanes, and HOT lanes were identified as the most beneficial strategies under both incident and non-incident conditions. As a result of ICM implementation, average corridor person flow increased by 6,860 persons per hour (37.8%) and 3,286 persons per hour (14.4%) under incident and non-incident conditions respectively.
The use of pricing to influence driver behavior through the HOT lane concept has been identified as a very important ICM strategy by most ICM initiatives. The evaluation of the impact of pricing in the ICM methodology developed in this research (as well as those developed for pioneer ICM sites) was based on long-term average mode and route shifts associated with pricing due to limited published knowledge on how tolls affect drivers’ decision to use/not to use HOT lanes in real-time. This research investigated how drivers responded to tolls using data from four HOT lane facilities in the U.S. The purpose of this approach was to determine if there is a general pattern in driver behavior in terms of their response to tolls. Analysis results revealed that, elasticity of HOT lane demand with respect to tolls is positive and statistically significant but inelastic (below +0.2). During peak periods, the elasticity further reduced to an average of +0.07. This implies that drivers’ decision to use/not to use HOT lanes is not greatly influenced by toll prices but by other factors such as travel time reliability, level of congestion, etc. The positive and inelastic relationship observed in this research goes against conventional wisdom that drives use of HOT lanes: tolls are supposed to discourage drivers from using HOT lanes. This suggests the probability that the tolls are not allowed to rise to a level where supply/demand can take place.
For ICM to be effective, it must be possible to anticipate the results of any implemented strategy. This research developed models to predict the demand for HOT lane use for each of the studied facilities based on tolls and changing traffic conditions. As expected, the performance of the model in predicting absolute demand wasn’t outstanding due to the weak relationship between HOT lane demand and tolls. However, the models fairly predict (about 70% of the time) the expected level of service conditions on HOT lanes.
