Feasibility of using freeway service patrol trucks as probe vehicles

This research assessed the feasibility of using trucks in an existing Los Angeles Freeway Service Patrol (FSP) fleet as probe vehicles to measure ambient speed on freeway segments. Floating car speeds were the basis of comparison with other speed data. Loop detector-based segment speeds and FSP truck speeds were compared against a common baseline. Unfortunately, FSP truck speed data available from the existing system are of insufficient quality to estimate ambient speeds. Comparisons between floating car and FSP truck speed records reveal that FSP truck speed is a poor measure of floating car (ambient) speed. FSP truck speed records underestimate floating car speeds overall, and covariance between the two is weak.