The introduction of electronic toll collection on the eight bridges crossing San Francisco Bay has provided the means for a relatively simple and low cost system for measuring travel times on many Bay Area bridges and roads. The toll tags sued for electronic toll collection can be read by readers at various locations on congested roads. The time of reading is recorded so that the time difference between when a vehicle passes one reader and passes the next can be computed. Such a system is already operating in Houston, where it is the primary source of travel time data. Capital costs per reader site where such systems have been implemented range from $18,000-$38,000 and for the operations center from $37,000-$86,000. Annual operating costs range from $4,000-$6,000 per detector site and $48,000-$96,000 for the operations center. The Bay Area bridges and their approaches are prime candidates for such a system. Most of the congested freeways and a few arterials near the Bay are also good candidates. The extent of the area for which toll tags would provide satisfactory travel time estimates will depend on how many vehicles choose to use electronic toll collection. This, in turn, will depend on Caltrans policies on tolls and the number of lanes available for toll tags and cash payment. Key words: Vehicle probes Travel time measurement Toll tags
