Friday, June 3, 2016

Appears to be working

A few months ago, the Lincoln Police Department implemented a new policy that encourages officers to take advantage more often of a state law that allows vehicles driven by suspended drivers to be impounded for 30 days. The policy change went into effect in late February, and provides an opportunity for a bit of evaluation research.

Since the policy is intended to deter suspended drivers, if it's working we would expect a decrease after implementation. Here's the problem: you can't simply count up the number of suspended driving tickets, because the overall level of traffic enforcement would influence that independent of the policy change. When officers are writing a lot of tickets, they are more likely to encounter suspended drivers then when they are writing fewer tickets.

Traffic enforcement activity by police officers varies considerably over time for several reasons, such as weather, service demands, and staffing levels. As an example, the peak month for tickets in 2015 was March, with 8,046 tickets (both warnings and officials), while the low month, December, produced 5,718. In order to account for these fluctuations, a good measure would be to calculate a percentage of tickets that yielded a suspended driver: suspended driving tickets divided by total tickets.

As the chart shows, that percentage takes a significant drop in the three months since the policy change. In fact, March, April, and May are the lowest months during the entire comparison period, which begins in January, 2013. If the percentage during the past three months had been the same as the average over the preceding 38 months, there would have been 159 additional suspended driving arrests from March through May.


I think this is pretty strong evidence that the policy is having the intended effect, although I'd like to watch it over a longer time period. Sometimes the impact of a crackdown initiative decays quickly over time. Officer Luke Bonkiewicz, whose research credentials are better than mine, is doing some more sophisticated work with these data. In particular, he is also looking at repeat suspended drivers. His work may shed even more light on the efficacy of impounding vehicles. Police practitioners ought to do this stuff more often: simple evaluations that, despite some methodological warts, provide evidence about what might be working (or not.)

7 comments:

Steve said...

You should try the same thing with automobiles that are not properly registered or licensed. It seems there are an awful lot of vehicles running around with no plates, and if they have an in-transit sticker at all it is expired. These people need to pay their fair share or get off the streets. It's more than likely they have no insurance either.

Can officers ticket someone that owns a car with no plates if it is parked on their own property?

Anonymous said...

So Armon Dixon and Timothy Claussen, both convicted rapists, escaped from LCC custody this morning?At least 4 hours ago. Is this out on social media yet?

Tom Casady said...

Yes, it was out pretty much as soon as NE Dept. of Corrections determined they were missing.

Tom Casady said...

Steve,

I agree with your observations, and there are lots and lots of tickets for fictitious plates, expired plates, improper registration. There is not, however, a specific State law that allows those vehicles to be impounded for 30 days, as there is for suspended driving. Since March 1, I've been reading almost all the reports on suspended drivers, and I have noticed that a healthy percentage of these orientated with an expired tag, a fake intransit tag, or a fictitious plate. The mobile data computer in the patrol car has drastically changed things since I was a street cop. You can run that plate at a stop light, or in a parking lot--right now.

Anonymous said...

Of course your policy is working Tom. Nothing you do ever fails, just look at all those numbers! You're the shining example of a man who should have retired 20 years ago. BTW, your also the reason LPD is dangerously understaffed. Ever publicly take credit for that fun fact? Have fun living with that.

Tom Casady said...

8:04,

I take it I won't be getting a Christmas card. BTW, not my policy, and was not my idea. Task force of citizens, prosecutors, and police officers came up with this plan.

Tom Casady said...

Steve,

Neglected your earlier question on cars parked on private property, like a driveway. Yes, if it is violation. Lincoln municipal ordinance 10.42.110 prohibits a person from having any vehicle parked outdoors for more than 30 days, even on private property, if it has not been registered at some point in time within the past 30 days. There is an exception for business premises where the vehicle is necessary for the operation of the business, farmsteads, and an exception if the owner has purchased a 6-month hobbyist permit, which costs $50.