Transportation system is one of key components in a nation's economic growth and it has significantly affected quality of our lives, especially with ever increasing urban traffic congestion. It is not surprising that public agencies try to optimally manage urban transportation system and every individual traveler tries to avoid congestions if possible. As an individual driver, route guidance or car navigation system that provides traveler with a shortest path based on distance or an alternative path during incident condition has been extremely useful. Even though it is more desirable to use travel times in providing route guidance, they are not readily available every roadway segment. Currently travel times are available for mostly freeway segments through toll tag readers, estimation algorithms using spot speeds, etc. With the Vehicle Infrastructure Integration (VII) initiative and user opt-in option, it is anticipated in a near future that individual vehicles equipped with VII can collect travel times and transfer such information to other vehicles and the transportation management system. Thus, travel time information for real-time route guidance can be available through the VII. This study explored system level potentials of the VII by evaluating various route guidance strategies within the VII environment. The study developed a simulation framework representing VII-enabled virtual world, and evaluated route guidance strategies with various factors including market penetration of VII-equipped vehicles, congestion levels of a road network, update intervals of route guidance information, drivers' compliance rates, etc. The study results clearly showed that VII-based route guidance significantly reduced travel time over no guidance case. Among four route guidance strategies, averaged link travel time-based guidance (ATG) produced best performance. Other key findings include (i) higher market penetration generates bigger benefits, (ii) multiple operations of competing route guidance strategies did not degrade the network wide performance, and (iii) prediction travel time based guidance (PTG) worked well for highly congested condition.
Abstract