Houston TranStar AVI Traffic Monitoring System
Introduction | AVI Technology
| How It Works
How It Works
The system uses vehicles equipped with transponder tags as vehicle probes. The main
source of vehicle probes are commuters using the "EZ-Tag" automatic toll collection system installed by the Harris County Toll Road Authority (HCTRA).
Transponder tag readers are placed at 1 to 5 mile intervals along freeways and HOV
lanes. Each reader senses probe vehicles as they pass a reader station and transmits
the time and location of the probes to a central computer over a telephone line. As the probe vehicles pass through
successive AVI readers, software calculates average travel times and speeds for
a roadway segment. The averages are made available to software which provides the
data for the Houston TranStar web site.
See an animated demonstration of the system.