Freeway Travel Time Data
BluFAX equipment has been used to collect travel time data for freeways and arterial sites at many locations throughout the United States and in Brisbane Australia.
I-95 Corridor Validation Study
The most extensive deployment was made for the purpose of validating GPS-based vehicle probe data procured by the I-95 Corridor Coalition from the Inrix Corporation in connection with its six-state Vehicle Probe Project. In all cases, the equipment performed flawlessly and provided reliable travel time measures. The initial testing for the I-95 Coalition project was on a heavily traveled 15 mile section of the Capital Beltway (I-495) near Washington, DC. Twenty units were deployed in connection with this data collection activity, were relocated to different sites as the data collection proceeded. Three data sets were developed in connection with these tests:
- Bluetooth data was used to represent "ground truth" due to its anticipated accuracy and large sample sizes.
- Floating car data, historically used to provide travel time data was collected and provide a check for the Bluetooth data
- GPS data acquired from Inrix, purchased on an area-wide basis by the I-95 Corridor Coalition.
Comparison of BluFax with GPS Data in California
Bluetooth Traffic Monitoring (BTM) technology was compared directly against travel times obtained from the toll tag system on a section of I-80 in San Francisco as shown in Figure 1. BluFax sensors were collocated with toll tag stations, data was collected over a period of two weeks, and travel time and speeds were compared directly. The experiment tested whether the sampling rate of BTM technology was sufficient to reflect accurate travel times and speeds as compared to toll tag derived data, and to test the percentage of vehicles sampled as compared to toll tags readers. Furthermore, the sampling rate was sufficient not only to characterize central tendency (mean and median) but also to estimate variance measures (standard deviation and percentile measures).
The figures below show data from a segment of Interstate I-495 between Washington, D.C. and Baltimore, MD between 6:30 a.m. and 12:45 p.m. Each data point represents the travel time from a matched detection at each end of the segment. The figure below depicts the impact on travel time as a result of an incident that began around 10 a.m., was cleared at approximately 10:50 a.m. and traffic returned to normal flow around 11:15 a.m.
