Freeway merge conflicts contribute significantly to freeway congestion. With the capabilities that will be available in an IntelliDrive environment, which enables vehicle-to-vehicle and vehicle-to-infrastructure communications, new approaches to managing freeway merges are possible. In this paper, an enhanced IntelliDrive enabled lane changing advisory algorithm was developed with a variable gap size concept. This algorithm first calculates anticipated lead–lag gap sizes with the equations of motion prepared for a car and a truck and for three vehicle dynamics (accelerating, maintaining current speed, and decelerating). The algorithm then provides lane changing advisories to freeway main-line vehicles (selected on the basis of the calculated variable gap sizes) to create more space within the ramp merging area. Evaluation conducted with a VISSIM microscopic traffic simulation model of a freeway network in Virginia showed that the proposed algorithm has the potential to address freeway merge conflicts. The maximum operational improvement observed was 6.4% higher average speed in the freeway main line within a merge area. Up to a 5.2% reduction in emissions was achieved. Further analysis conducted in terms of the sensitivity of algorithm performance to driver compliance rates suggested that a very high compliance rate (90% or higher) was necessary for the proposed algorithm to work as intended.

Many states have implemented truck lane restrictions in an attempt to improve safety and mobility on freeways. These restrictions typically prohibit trucks from traveling in the median (left-most) lane of multi-lane highways; the restriction potentially increases passing opportunities and reduces negative interactions between slow-moving trucks and faster-moving vehicles. Virginia has restricted trucks from the median lane of some interstates with three or more lanes by direction since 1997, but no systematic evaluation of the safety impact of the restrictions has been conducted. Evaluations of similar restrictions in other states have yielded contradictory findings, but those studies often used a limited data set. An empirical Bayes’ analysis of Virginia's restrictions was performed by using 6 years of crash data from 22 sites with restrictions and 16 similar sites without restrictions. The analysis showed that a breakpoint in safety performance occurred around 10,000 vehicles per day per lane. Facilities where the volume was below this threshold had significantly fewer crashes than anticipated, averaging a 13% reduction in total crashes and a 32% reduction in fatal and injury crashes. Sites where the volume exceeded this threshold had increases in total crashes and fatal or injury crashes of 28% and 23%, respectively. A detailed analysis of crashes on the higher-volume roads was conducted to screen out crashes in which the restrictions likely played no role. That analysis showed that the number of truck-involved crashes was still significantly higher than predicted, indicating that safety on higher-volume roads may be negatively affected by truck lane restrictions.

Rail–truck intermodal terminals can play a key role in making rail–truck intermodal transportation an effective transportation alternative to long-haul trucking. To measure this effectiveness, public and private stakeholders require some qualitative and quantitative methodologies. This paper is based on a study describing a general methodological framework for evaluation of the impacts of intermodal terminals on the transportation system and applying it to the highway system of Virginia. Apart from incorporating the needs of several agencies into the framework, preliminary models for site-specific evaluation of impacts on mobility, accessibility, safety, and economic activities were also developed, and were calibrated with commodity flow, socioeconomic, and other data for the Commonwealth of Virginia. Results of the application of the evaluation framework on a case study terminal are presented in this paper. The study identified the key steps involved in the assessment of highway system impacts and regional planning of intermodal terminals in Virginia. It is recommended that further research be carried out on a detailed evaluation to provide decision support on the feasibility of public–private shared financing of intermodal terminals.