Probe Vehicle Data Sample

• Time vs. distance.
• Speed vs. time.
• Speed vs. distance.
• Travel time vs. starting time.

• The plots are for the 6th run that the probe vehicle did during the morning shift.
• The probe vehicle started from the northern most point on the freeway and then drove the southbound section and then turned around and drove the northbound section. This means that each of the plots below has the southbound and northbound sections in it.
• Since both southbound and northbound runs are on the same plot, you should first see the loop detectors in the southbound direction and then see them in the reverse order after the vehicle turns around and drives northbound.
• The small boxes are where the drivers pressed a key to indicate that they were passing an incident. We don't know which incident they were passing - just that it was one.
• The small "x"'s are where the vehicles drove over the INRAD points. The INRAD system is an inductive radio system the vehicles picked up when they drove over it. It was installed at specific locations in the road and we used it to pinpoint the location of the vehicles.

Density from loop data:

Time vs. Distance

This graph shows us the time vs. distance of the probe vehicle. Note that the inverse of the slope of the line is the speed. So the steeper the slow, the lower the speed. If you look at the 6 or 7 mile mark you can see that the probe vehicle was going really slow for around 7 minutes. But right after it passed the incident it sped up. The steep section at the 9.5 mile mark is where the probe vehicle got off the freeway and turned around.

Speed vs. Distance

This graph shows us the speed vs. distance of the probe vehicle. The verticle lines are the loop detector locations. The numbers that are over the verticle lines are the loop detector numbers. There is a map of the freeway on-line. You can see that on the southbound section (the first section) the probe vehicle slows down quite a bit between loop detectors #19 and #17. If you look on the density plot above you will see that this is exactly what the loop detector data says as well. The section in the middle where the speed drops to zero is where the probe vehicle turns around.

Speed vs. Time

This graph shows us the speed vs. time of the probe vehicle. Once again the horizontal lines are the locations of the loop detectors. Since the vehicle is travelling different speeds and hence takes a different amount of time to move from detector to detector the spacing between loop detectors varies quite a bit. If you look at the detectors in the southbound direction (which is the first set of loop detectors) you can see that between 9:03am and 9:10am the vehicle is travelling very slowly - around 10 mph. You should also notice that the loop detectors are widly spaced due to this. After the vehicle passes the incident at loop detector #4 it speeds up rapidly.