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nikipedia's avatar

Why do police officers leave their cars idling?

Asked by nikipedia (27531points) September 27th, 2010

I just asked some and they said they have equipment in their cars that needs to be on at all times. Is this true? What equipment? Why? Wouldn’t it be cheaper to just get a battery? Gas isn’t free.

I told them it was bad for the environment. They looked stunned and told me smoking is bad for the environment too. Then I looked confused and told them I don’t think anyone should smoke, either. It was not a very productive exchange.

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23 Answers

janbb's avatar

I had the same exchange with some construction workers with the same result. I imagine the police may have to leave their radio on; I don’t think the construction workers have any such excuse.

JilltheTooth's avatar

Some of the big construction rigs use more fuel restarting than idling for awhile. I heard this awhile ago, please don’t ask me for confirmation, I can’t supply it…

wundayatta's avatar

I think the police need to be able to drive off instantly when called on. It saves them time from having to start the engine, which also may not start right away.

BoBo1946's avatar

I’ve invited John Pennington to answer this question. He certainly can tell us.

ucme's avatar

Maybe they’re worn out & in need of ar-rest! Good God, did I just say that out loud? I apologise, do carry on.

Seek's avatar

Same reason my county Sheriff bought three hundred brand new cruisers without hiring officers to fill them – because he’s the Sheriff and he can use your tax dollars however he goddamn feels like spending them. Who’s going to tell him not to?

mcbealer's avatar

In order to avoid tons of wear and tear to the starter and ignition.

It’s also safer:
– lowering response time on new calls where every second counts

– their jobs require constant vigilance, and having their equipment ready to go at all times is a part of that mentality

woodcutter's avatar

I think all the electronic equipment like computers run down a battery quickly if let set too long without the engine running to keep the charge up. There’s a lot of crap in those cars. That’s why you might see them with their hoods up if they are stationary for a prolonged period so the engine won’t overheat.

nikipedia's avatar

If this is a matter of “every second counts” then wouldn’t it be more valuable for them to be sitting in their idling cars drinking their coffee rather than Starbucks?

I have started a car an estimated 5,000 times in my life, and that’s a conservative estimate. (Nine years of driving minus two years of not owning a car, assuming two starts per day = 7×365 x 2 = 5,1110), so I’m going to consider myself reasonably well-versed in the process of car starting. It involves the following steps: (1) locate keys, (2) insert into ignition, (3) turn key, (4) put car in gear.

Since these are police cars with presumably no risk of being stolen, you could even leave the keys in the ignition, eliminating the process of finding keys or putting them in the ignition. Further, whether the car is left idling or not, you still need to put it in gear. So leaving the car idling only eliminates the physical turning of they key, which I would estimate takes me approximately half a second. Let’s be generous though, and call it a full second.

Now, let’s say the distance from the closest seat to the door in Starbucks to the door of the police car is… 50 meters? That would take Usain Bolt, the fastest man on earth, 4.79 seconds, assuming the same pace as his world record 100m time of 9.58 seconds. And let’s not forget opening the Starbucks door (maybe 1.5 seconds?) and opening the car (another 1.5 seconds?)

So all said and done, if these police officers were the fastest men on earth AND they had access to the seats nearest the door, sitting in the Starbucks is still tacking on 7.79 seconds, which is more than SEVEN TIMES longer than the process of turning the key that is already in the ignition. I don’t think the “every second counts” argument holds much water, here.

jerv's avatar

You are neglecting thermal stress. Shutting the engine off allows things to cool and contract, only to expand again when the engine is running and hot again. Over the lifetime of the average cruiser, which sees heavier use than your car ever will for more years than your car will last, it adds up and breaks things.

If they shut it down all the time, your taxes would be paying for new engines and exhaust systems far more often.

Simone_De_Beauvoir's avatar

Because they can get away with it.

nikipedia's avatar

@jerv: I asked an engineer friend to estimate about how much gasoline their cars use while idling. He said about 1.7 gallons/hour.

Assuming the cars idle for approximately 2 hours per day, 365 days per year, at $3.00/gallon, thats:

1.7×2 x 365×3 = $3,723 per year. How much does a new engine cost? I honestly don’t know, but even if it was $10,000, this idling policy would have cost more than a new engine after four years.

bob_'s avatar

Because if they don’t, then the terrorists have already won. Also, because they’re lazy.

@Seek_Kolinahr Aren’t sheriffs elected?

Seek's avatar


Don’t go there.

My county is full of old Southerners who have never voted for someone who didn’t have an ”(R)” after their name on the ballot. Yes, they are stupid enough to keep voting in this jackass every single election, no matter how much better the guy running against him is.

There are actually three Republican seats on the county commission that are going unchallenged this year. That’s how pointless it is to bother running as a Democrat.

bob_'s avatar

@Seek_Kolinahr Ah, right. Too bad.

jerv's avatar

@nikipedia Modified engines aren’t cheap, and for years is rather optimistic. When you add in the cost of downtime or having to buy extra cruisers to cover for them (and no, they are not the cars you see in the showroom; they start at $42k and go up from there), you are still ahead. Even buying one extra cruiser will wipe out your entire gas savings and leave you a few thousand dollars in the hole when the car is retired after ten years (the maximum permissible, at least here).

Oh, and just because you find a crate engine for $8k, it takes time to put it in. At $100–150/hr, a two day job can get pricey.

I’m sure bean-counters at the precinct have done the math and would’ve put a stop to it if it really were cheaper to shut them down, so you don’t have to take just my word for it.

nikipedia's avatar

@jerv: But the cost of a new car is irrelevant. What we’re talking about is reducing the lifespan of the engine. And if the cars are being retired after ten years anyway, is turning the engine off and on plausibly going to reduce the engine’s lifespan to <10 years? Like, supposing all that turning on and off has the very severe problem of reducing the car’s lifespan by, say, 5 years. If the engine was going to last for 15 years and you knock that down to 10, you’re breaking even anyway. And those ten years of idling gas cost you $37,230!

I guess I don’t trust that these bean-counters have done the math. I think they’d rather waste money on shit that makes cops feel powerful and important, and fuck the environment.

jerv's avatar

@nikipedia Fleet cars are not like normal cars, so you really can’t compare. Normal people don’t put the sort of station on their cars (and engines) that cops, taxi drivers, and delivery drivers do. Have you ever replaced a flywheel? As it is part of the transmission, it is also expensive and time consuming to replace. That is why I laugh at hyper-milers; all of their gas savings disappear every couple of years, and what is the environmental impact of casting and machining a replacement? Of course, they doesn’t look upstream. Do you know how much pollution is generated by manufacturing replant parts?

Also since 37 < 42+, you are still losing money.

nikipedia's avatar

@jerv, no, you are missing the point. According to your own statistics, after ten years, you must replace the car anyway. So that $42,000 is already spent. On top of that $42,000, you are also spending $37,000 on wasted, idling gas.

At that point, you are already replacing the entire car, whether the engine has worn out or not. So that also eliminates any argument about pollution relating to replacement parts.

The only way your argument holds up is if the engine would likely have died before the ten year mark, and idling is required to preserve it beyond that. Even then, using the most extreme case of your figure ($8000 engine + 16 hours of work at $150 per hour = $10,400) the engine has still paid for itself in idled gasoline within four years. You are correct to point out that manufacturing contributes some amount of pollution, but I do not have any information regarding whether this is more, less, or equivalent the pollution generated by an idling car (which is substantial). Keep in mind that 20% of electricity in the United States comes from nuclear power, which, while not perfect, does not generate the kinds of emissions that fossil fuels do.

jerv's avatar

@nikipedia Okay, lets say you need to have twenty cars on the road at all times. No matter what. That means that you will have a fleet of at least twenty-two to account for accidents and normal mechanical failures.

Now, if you are pulling them in for repairs more often, that means that you are going to have more “reserve” vehicles to cover as you are more likely to have one in the shop at any given time. Last I checked, twenty-four cars cost more than twenty-two, all else being equal, and that is another $84,000-plus in addition to the increased costs associated with a larger fleet.

If you can reduce downtime due to maintenance/repairs, you can get by with fewer vehicles. Buying fewer vehicles is cheaper than buying more vehicles, and that puts us back to $37K < $42K. There is also the fact that the maintenance isn’t free, so don’t forget to add that into your calculations.

Do you see where I am coming from now? You seem to still be thinking in terms of the number of cars in the average American’s driveway, which is considerably fewer than the number of cruisers in the average precinct. And unlike you or I, they can’t just get a loaner car. I mean, have you ever seen a car at Avis or Enterprise that can handle driving all day (not just eight hours straight, but all twenty-four) with rims rated for a 40MPH curb impact and with a rear cage to prevent the back seat passengers from strangling the driver? Fleets are entirely different than individual vehicles, and police fleets are different from commercial fleets (taxi, delivery…) so you have to think differently.

wundayatta's avatar

@nikipedia You’re talking as if cops are scientists.

Cops have to be dragged, kicking and screaming, into anything that involves using actual data to improve their work. Things have worked this way just fine for 100 years. There’s no reason to change, now.

john65pennington's avatar

Up until recently, police cars were left idling for several reasons. one, a K-9 officer and his dog in the summer is self-explanatroy. two, in order to maintain a computer connection. three, for an immediate response to an emergency situation.

All of the above had been instituted for many years, until the a new law was passed. this law forbids the leaving of an unattended vehicle with the engine running or not running and the keys in the ignition. the powers that be decided that only part of this law pertained to police vehicles and this was the section pertaining to K-9 officers and their dogs. this was still allowed for the non-abuse of the K-9 dog, especially in hot weather.

Keep in mind this law only pertains to Tennessee. other jurisdictions have their own laws and regulations.

Sorry for the delay in answering your email. i just noticed your question.

jlm11f's avatar

@nikipedia This question right here (including that exchange you had with the cops) is why I love you.

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