Saturday, 10 December 2022

Fleeing drivers respond to incentives, but that doesn't mean that the current policy settings are wrong

The New Zealand Herald reported earlier this week:

Nearly 10,000 people in vehicles fled from police in the past year - more than double the number recorded prior to the police changing their pursuit policy nearly two years ago.

At the same time, the number of those behind the wheel not identified has nearly tripled, while those being held accountable have stayed the same.

These are the key reasons Police Commissioner Andrew Coster referenced in announcing recently that the police pursuit policy would be reviewed next year and a Fleeing Driver Framework introduced...

Between 2010 and 2020, 75 people died in police chases, and two in incidents when police did not pursue.

In December 2020, after a major police review, staff were told a pursuit was only justified when the threat posed by the vehicle prior to failing to stop, and the necessity to immediately apprehend the driver and/or passengers, outweighed the risk of harm created by the pursuit.

In the nearly two years since, there have been no deaths during pursuits, while four people have died in incidents after fleeing from police.

Meanwhile, data released to the Herald shows over that over the same period the number of fleeing driver incidents increased from 4846 - in the 12 months prior - to 9499 in the 12 months to November this year.

The number of incidents where the offender was not immediately identified nearly tripled, from 2419 to 6412, while police proceedings remained relatively steady, moving from 3374 to 3484. 

When the police decide to stop a vehicle, the driver of that vehicle has a choice: they can stop, or they can flee. The economist Gary Becker described a rational theory of crime that can help us understand the driver's choice. In Becker's theory, a rational driver would consider the costs and benefits of fleeing, and if the benefits outweigh the costs, they would choose to flee. When the police have a policy that reduces the chance that they will pursue a fleeing driver, that increases the chances that a driver will escape any punishment. That increases the benefits of fleeing, meaning that more drivers will choose to flee. Not all drivers will choose to flee, because some drivers are more susceptible to the social and moral costs of bad behaviour, but more drivers will flee than if the police were more willing to engage in pursuits. So, it should be no surprise that we have observed more fleeing drivers.

However, just because there are more fleeing drivers, that doesn't mean that the policy is a bad policy. Each policy comes with benefits, and costs. The current (since December 2020) police policy has resulted in no deaths during police pursuits, compared with 75 over the prior ten years. That suggests a benefit of the policy might be around 15 lives saved over the two years that it has been in place. How much benefit is that? The Ministry of Transport uses a value of a statistical life of $4.88 million in measuring the benefits of road safety. Using that value for each life saved as a result of police not engaging in pursuits, the benefits of the policy change might be as much as $73.2 million. That's not all of the benefits of the policy change though, as it doesn't take into account benefits from reductions in non-fatal injuries, or damage to vehicles and other property resulting from fewer pursuits. The estimate of $73.2 million in benefits is clearly an underestimate, but useful as a benchmark.

What about the costs of the policy? There have been more fleeing drivers, and police proceedings have not increased. So, that means that more drivers have gotten away with whatever it was they were going to be stopped by the police for doing. That leaves those drivers free to do more of those activities, and that has a social cost. Perhaps that means more speeding, unsafe driving, and other traffic violations, but also more stolen vehicles, which can be used in committing other crimes.

To assess the cost of the police non-pursuit policy, we need a sense of the costs of those additional social harms. One example that has been raised is ram raids, which have increased concurrently with the change in police pursuit policy. Focusing just on ram raids, this Police OIA response suggests that there were about 250 ram raids in the first six months of 2022, a 500 percent increase over 2018. This Stuff article provides the costs to a retailer of two instances of ram raids ($13,500 and $15,000). Combining those figures suggests a social cost of ram raids of about $12.5 million (scaled up to two years). That assumes that all of the ram raid increase is purely due to the change in policy pursuit policy, which is unlikely. However, it doesn't take into account any of the other non-ram-raid increases in social harm that may have arising due to more fleeing drivers. Clearly, the total cost of the policy is going to be more than $12.5 million over two years. The key question is whether all of those other social harms add up to more than the additional $60 million that would offset the value of lives saved in pursuit-related crashes that didn't happen.

Coming back to the New Zealand Herald article, the Police are being forced into a rethink of their current approach to fleeing drivers:

[Police Association president Chris Cahill] said while the policy needed to be reviewed, it could not ignore the fact there were no deaths.

“We don’t want to go back to a situation where people are dying in fleeing driver incidents. Family of those that are killed are also seriously impacted, and so are our members involved.

“That’s why you can’t say the policies are a complete failure.”

But Cahill said it would appear the balance isn’t “quite right”.

It seems to me that the balance may be already right. Pursuing more drivers will increase the risk to other road users, and the benefits that arise from more pursuits seem far too low to be worthwhile. Perhaps the review of the policy will enable the Police to examine the costs and benefits of any change to the policy carefully. The numbers I pulled together in this post were based on 15 minutes of casual web searching. A more thorough approach would give much greater confidence (although I doubt that the conclusion would change).

Finally, I thought that as a country we were supposed to be taking a 'road to zero' approach to road safety - given that we have now experienced zero pursuit-related deaths for a couple of years, isn't a resumption of police pursuits a road away from zero?

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