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South Salt Lake Journal

Police department uses new device to record traffic speeds, flow

Mar 30, 2020 01:34PM ● By Bill Hardesty

SSLC PD is using the Jamar Black Cat II for traffic enforcement and crash investigations. (Courtesy of SSLCPD)

By Bill Hardesty | [email protected]

Big news! The South Salt Lake Police Department has two Jamar Black Cat II radar recorders and they’ve been using them over the past couple of months. They were paid for with a grant from the Utah Highway Safety Department.

“This device gives us real time data, and it is cool,” Police Chief Jack Carruth said.

How it works

The recorder is attached to any pole and records the speed of vehicles passing by. While no individual data is collected, it does give a picture of how traffic flowed on that street during any given time.

It can also record the length of vehicles. This feature is used when a resident complains about oversize trucks on a prohibited road. The data shows a pattern of truck behavior and police can be sent to resolve the issue.

The box looks like any other utility box. The devices are moved around the city depending on residents’ traffic complaints or for a crash investigation.

Traffic complaints

Traditionally, there were three possible responses to a resident’s traffic complaint. Each of these responses has issues.

The first response is to send out an officer to sit in the area and observe traffic conditions. While this has helped at times and maybe even some citations are given, the problem is how long can the officer sit. Most likely no more than two hours. In addition, the presence of police certainly affects drivers’ behavior, or in other words, they slow down.

The next response is to set up a speed trailer. This device informs a driver how fast they are going as compared to the speed limit. The hope is that such information will make the driver reduce their speed to match the speed limit, which might be true. However, it alters drivers’ behavior. There are studies to show that some drivers speed up to see how far they can make the gap, or they slow down only around the trailer. An additional problem is the risk that the devices will be vandalized if left overnight.

The third response is to place a speed tube across the road. Like the other responses, the discovery of the tube alters drivers’ behavior resulting in inaccurate data. A tube requires public works involvement and damages the road surface.

“The Jamar gives us a clear picture of traffic,” said Officer Chris Taylor, a crash investigator with SSLCPD. “The information is accurate and unbiased.”

Now, the traffic division can put an officer on site during the times when speed violations are likely happening.

“It gives us the best time to apply resources,” Taylor said.

For example, a resident complains that people are speeding on 300 East. Taylor comes out and attaches the Jamar to a pole for a week. Afterward, he can pull the data and know that drivers are likely to speed between 8 and 10 a.m. Monday through Friday. Given this information, the traffic division can place an officer on 300 East during these times.

“Our job is to correct bad driving behavior,” Taylor said.

Crash investigation

The Jamar is used in crash investigation to provide unbiased data on the speed of the road.

Taylor provided two examples.

In the first example, a driver traveling 9 mph over the speed limit causes a crash with serious injuries. The city prosecutor is trying to decide if they should add a count of reckless driving to the charges. Taylor uses the Jamar to monitor traffic along the stretch of the road the driver was traveling for a week. The data shows that given the time of day most drivers drive 9 mph over the speed limit. Given this information, the city prosecutor doesn’t add the reckless driving count because the driver was only driving with the flow of traffic.

In example two, a driver is going 45 mph in a 25 mph speed limit zone and causes a crash with a fatality. Now the question is how reckless was the driving? Should a count of murder be added to the charges? After the Jamar study, it is shown that the average speed on the road was 34 mph. The data shows that the driver was driving much faster than everyone else and maybe a count of murder is warranted.