Knowledge Resources

Traveler information is becoming increasingly important as travelers expect reliable, up-to-the-minute information on traffic conditions that may affect their commutes. San Antonio wanted to add arterial travel speeds to improve its existing traveler information system. Traditionally, arterial information is collected as point-speed data determining traffic conditions at a specific point and not between points, which has proved to be ineffective in determining travel times over a length of roadway. San Antonio decided to deploy Automatic Vehicle Identification (AVI) tags to collect arterial information. This system measures travel time between points, displaying data through web sites and variable message signs. Tags for the project were distributed among travelers on a voluntary basis.

Although the system San Antonio deployed never fully met expectations due to insufficient market penetration, the project had technical merit and provided valuable lessons learned that might be useful to other cities considering similar deployments.

• Distribute tags in a way that will reach the most drivers. The project team considered several options for distributing vehicle tags. San Antonio's first choice was to distribute tags through the Department of Motor Vehicles (DMV). These tags would be embedded within the vehicle registration tag and distributed during annual registration. Even though distributing tags in this manner would reach a much larger target of vehicles, DMV was not able to manually distribute the tags only to the county where the project was being implemented. Another vehicle tag technology was chosen and a voluntary program was put in place for distribution. This method resulted in less than 10 percent of vehicle tags being distributed than what was needed to produce adequate results. Technically the system was capable of producing accurate travel times, but it was difficult to provide consistent travel time readings because the low level of market penetration made it difficult to measure travel times consistently throughout the day. A higher concentration of AVI tags would provide more consistent data throughout the day.
• Consider using electronic toll tags if the region has toll roads. San Antonio does not have existing toll roads, therefore they were unable to use existing toll tags. They believe that an area with existing toll facilities would provide a great opportunity to make use of these tags to provide travel time data along arterials. If electronic toll payment is employed in an area, these tags can be used to collect travel times and the costs to implement a travel time system would be reduced.

The public seems to want arterial information to supplement major freeway traveler information. One method of collecting this information is by using vehicle tags and readers to measure travel times. The project undertaken by San Antonio was a good opportunity to determine the advantages and disadvantages of deploying an AVI tag system along arterials in an area without existing tolls. San Antonio's experience has shown that vehicle tags are technically capable of collecting accurate and reliable arterial travel times, but only if an adequate level of market penetration is achieved. A system that provides accurate and reliable arterial travel times can improve customer satisfaction, safety, and mobility.