Instruction manual

Appendix E.2 Extra Axles

This error, while not frequent, does happen. It is almost always a problem with the actual road tube installation, or with

the road surface. Causes of extra axles are listed below:

 Road Tube Bounce (slap).

Since the road tubes are made of flexible rubber, they move when they are hit. Depending on how tightly they

are stretched, how far apart the anchors to the roadway are, and how heavy the vehicle crossing the road tubes

is; the road tube may move only slightly, or it may move a lot. When a tire hits the road tube normally, the air

switch is activated by the sound of that tire. If the road tube is moved a lot, it will return quickly enough to its

original position and may “slap” the road tube with enough force to actually “sound” like another axle.

This error is minimized by the fact that the air switch will not re-activate for at least 33ms, and the road tube

should be stabilized by then (but not always). You can also help this problem by tapping the road tube on the

road at short intervals along its length.

 Rutted Pavement.

DO NOT INSTALL ROAD TUBES OVER BADLY RUTTED PAVEMENT. This will cause the road tube to

bounce widely when driven over by heavier vehicles. If you must install the road tubes in rutted pavement, tape

them down securely.

 Road Tubes Not Perpendicular to Traffic.

This error (usually only at slow speeds) is caused by a vehicle not hitting the road tubes squarely. If the vehicle

is going slow enough, the left tire(s) and the right tire(s) will cause an individual activation. This problem is most

commonly seen in intersections, where vehicles are turning across the road tubes at slow speeds.

Appendix E.3 Bad Speed and/or Length

This problem is infrequent, but can occur sometimes when the counter misses axles. For example, assume a 2 axle, 8

foot axle spacing vehicle traveling 60 mph crosses two road tubes spaced 8 feet apart. The spacing and timings

occurred as below:

1) Road Tube #1 hit by first axle at 10:00:00.00000.

2) Road Tube #2 and #1 hit almost simultaneously by the first and second axles at 10:00:00.09090. Counter

missed the Road Tube #2 hit (for whatever reason).

3) Road Tube #2 hit by second axle at 10:00:00.18181.

Since the counter waits for the first hit on #1 and the first hit on #2 to determine the speed, the speed will be determined

by the second road tube #2 hit. This gives (8ft/.18181sec) = 44 ft/sec, or 30 mph. This is only ½ the actual vehicle

speed! Since the speed is calculated wrong, the counter will also give an incorrect length value for the vehicle.

Note that this error is from the data, so it gave the values it could.

Appendix E.4 SnMis (Sensor Miss) for Entire Vehicle

Like the previous error, this problem only occurs as a result of missed axles. “SnMis” (for sensor miss) is the Phoenix

II’s way of indicating that did not have enough sensor data, or got sensor data not in the right order to make a vehicle.

Once a sensor miss occurs, the Phoenix II block out all further sensor activations on that lane for 1 second.

 SnMis #0 occurs only with Axle-Loop-Axle or Loop-Axle-Loop combinations. This error indicated an improper

sequence of sensor activations or missing one or more activation(s).

 SnMis #1 is that the counter only got a road tube #1 strike, with no further road tube activations. This can

happen if a vehicle hits the first road tube, but misses the second while changing lanes.

 SnMis #2 is that the counter only received a road tube #2 strike, without first getting a road tube 1 strike. This,

like SnMis #1, can happen if a vehicle crosses into the lane but misses’ road tube #1.

 SnMis #3 is an over speed or under speed vehicle, and can optionally be used to indicate vehicles which only

hit road tube #1 and road tube #2 once, with no further activations. Note that the counter will normally turn

these types of activations into two axle vehicles with the axle length equal to the sensor spacing.