A-7
Low Speed Data Collection
The default settings of the TRAX are designed to accurately collect traf-
fic data at speeds ranging from 10 to 70 mph. In these situations, data can
usually be collected without making any adjustments to the settings of the
TRAX.
However, the TRAX Apollyon Plus II is capable of recording vehicle data
with a high degree of accuracy from as low as idle speeds to 10 mph. If
you are attempting to collect data at locations where speeds will be very
low (such as driveways and parking lots), adjustments should be made to
compensate for the speed of the vehicles being recorded. The following
guidelines should be used for these applications.
Dead Time (DT)
When recording traffic with road tubes, there is always the possibility that
the tires from each side of an axle will hit the tubes a fraction of a second
apart, either from the road tubes being slightly angled or from the vehicle
being slightly angled as it hits the tubes.
The Dead Time setting is used to keep these extra hits from showing up as
additional volume in the data. This setting allows you to set a specific time
in the TRAX when it will not accept a new pulse from the road tube after
it has just received a pulse. At normal traffic speeds, the time from one tire
of an axle hitting the tube to when the other tire from an axle hits the tube
is usually just a few milliseconds. However, this time increases the slower
vehicles are moving.
In the TRAX, the DT is typically set at 20 to 40 milliseconds for normal
traffic, as this will cover most speeds. Speeds from idle to 10 mph will
require the DT setting to be increased.
When recording traffic in a very low speed situation, use a DT setting of
200 to 300 milliseconds to avoid double counting. Whenever you adjust
the DT setting, we recommend that you watch the TRAX as a few vehicles
are recorded to be sure the TRAX is recording correctly.
NOTE:
Be sure to reset the DT setting once you have finished your low
speed counting. Using an incorrect DT setting for normal speed traffic will
produce incorrect data.
Appendix
Summary of Contents for TRAX Apollyon Plus II
Page 1: ...i Automatic Traffic Data Recorder User s Manual JAMAR Technologies Inc TRAX Apollyon Plus II ...
Page 24: ...TRAX Apollyon Plus II User s Manual 1 18 ...
Page 46: ...TRAX Apollyon Plus II User s Manual 2 22 ...
Page 47: ...3 1 Chapter 3 Road Tube Installation Chapter 3 Road Tube Installation ...
Page 52: ...TRAX Apollyon Plus II User s Manual 3 6 ...
Page 53: ...4 1 Chapter 4 Road Tube Layouts Chapter 4 Road Tube Layouts ...
Page 70: ...TRAX Apollyon Plus II User s Manual 4 18 ...
Page 71: ...5 1 Chapter 5 Troubleshooting FAQ Chapter 5 Troubleshooting FAQ ...
Page 75: ...A 1 Appendix Appendix ...