# What do police "investigate" in a car accident? **URL:** \ **Category:** Factual Questions\ **Created:** [August 3, 2020, 4:24pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172 "2020-08-03T16:24:56Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [August 4, 2020, 12:25am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/21 "2020-08-04T00:25:01Z")
> [@Dinsdale](#): > > I readily acknowledge that if the cops do not perform that investigation, it will be impossible to recreate later. > > I’m sure this is too simplistic, but a truck crashes into a car in heavy traffic. Someone (likely several someones) stuck in that traffic behind the crash was a front row witness. Either the truck did something wrong, or the car did, or they both did. Or maybe there was equipment failure. Plenty of time to take breath/blood samples for drugs/alcohol. How much and what kind of evidence would elude a good thorough video of the scene, then cleaning things up and moving the vehicles to the side of the road as quickly as reasonably possible? How much would this sort of evidence affect eventual insurance claims/civil litigation? Maybe the Buick driver brake-checked the truck. Maybe the Buick driver had a medical emergency & swerved/crashed into the truck. In those two scenarios the Buick driver has fault in causing the accident which would probably reduce the civil payout; possibly even cause the trucking company to _receive_ compensation instead of pay it. Maybe there was a third vehicle that clipped the Buick, sending it careening out of control right into the path of the truck (youtube PIT maneuver to see what a cop car can do to a fleeing suspect by gently nudging the rear end of the fleeing vehicle.) Chances are the other vehicles with the best vantage point were doing their own dodging to avoid vehicles suddenly not in their own lane anymore & didn’t realize how bad the accident was from their rearview mirror, or there was no shoulder they could safely pull over to, either because of a lack of a shoulder there or other traffic between them & the shoulder so they continued on. Or they were late to work. Or they have an outstanding warrant & would rather not give the police their information. Or, or, or…the point is the PD may not have the best independent witnesses Maybe the police wanted to wait for daylight &/or the sun to be high enough to not cause unduly long first light shadows on the road. They can, & sometimes will close a road after the fact to recreate an accident scene but when they do that they’ve already lost the original skid marks & impact points. I’m sure you’ve seen a tight curve on an entrance or exit ramp with lots of impact marks. One might be able to tell exactly where the current accident’s impact was by things like concrete dust that will blow/wash away in the coming hours/days/weeks. So sorry you were inconvenienced a bit but some family lost a loved one today & some truck driver has to live with the guilt that he may have caused someone to die; think about the weight off of his shoulders if an investigation reveals that it was **not** his fault. Further comments about you & your being inconvenienced belong in the Pit. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [August 4, 2020, 12:28am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/22 "2020-08-04T00:28:07Z")
We recently had a roadside accident where 4 police officers at a traffic stop were killed by a truck. They kept that freeway closed for 24 hours. 4 deaths is a very severe traffic accident, but when it’s not police officers, the road isn’t normally closed that long. There’s a synchronicity about that road closure: the road has to be closed while police measure and photograph, because wandering around on the road is dangerous. But our police are particularly blasé about wandering around on the road, expecting their uniform and badge to keep them safe, and indifferent to the effect on traffic – which is part of the reason why the police memorial contains mostly the names of officers killed in road accidents, including the four just killed while standing in the freeway slip lane. ---
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [August 4, 2020, 2:08am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/23 "2020-08-04T02:08:24Z")
> [@Spiderman](#): > > So sorry you were inconvenienced a bit but some family lost a loved one today & some truck driver has to live with the guilt that he may have caused someone to die; think about the weight off of his shoulders if an investigation reveals that it was **not** his fault. Further comments about you & your being inconvenienced belong in the Pit. You miss the point. I was exceedingly minimally inconvenienced. Hundreds (if not thousands) more were far more inconvenienced - standing still on the expwy for hours. That adds up (in this pitworthy scum’s opinion.) ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [August 4, 2020, 9:55am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/24 "2020-08-04T09:55:12Z")
Some years ago, I was driving a large truck on a rural dual carriageway and was stuck in a jam. We moved forward slowly until I came to the scene of an accident, Our side was blocked by wrecked vehicles (a van had entered the main road from the side and got T-boned by a car) All smaller vehicles were being diverted onto country lanes, but I and several others were unable to follow them. There were two police cars and a fire/rescue vehicle there - the ambulance(s) were long gone, and nothing was happening. I spoke to the sergeant in charge and suggested that we could cross the median and pass on the other side, but she would not allow it. An hour later the accident investigators turned up and started measuring. This took well over an hour until the investigators finally allowed the clear-up crew to sweep the road and let us do what I had suggested. My feeling was that the sergeant was fairly new and lacked the confidence to make a decision, even though letting us pass would not have disrupted the scene in any way. ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [August 4, 2020, 12:14pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/25 "2020-08-04T12:14:37Z")
OP: Why the quotation marks around _investigate_ in the thread title? The police actually do investigate accidents. AFAIK, and especially the state highway patrol, large enough police departments have specialist accident investigators. They’re not in it for an easy shift or just some overtime. It’s quite complicated and, as mentioned above, exacting. ---
**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\ **Post date:** [August 4, 2020, 12:19pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/26 "2020-08-04T12:19:18Z")
Are you sure it wasn’t a shootout instead of an “ordinary” accident? We have our share of expressway shootings. In that case, it’s a crime scene, and a whole extra set of protocols come with that. That closes things down for quite a while. “Several hours” is a long time. For examples, that could involve the spilling of toxic chemicals, or a livestock shipment that got loose and is running amok on the expressway. Reasons vary. ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [August 4, 2020, 12:34pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/27 "2020-08-04T12:34:20Z")
There is another aspect that has not been mentioned at all. Gathering evidence is not only for legal purposes, it may also be used to determine if other measures such as traffic management controls could have prevented the incident. It’s just a fact of life that some road layouts are inherently dangerous, or the road environment is dangerous - such as having bridge supports close to live traffic lanes, trees close to roadside - especially at predictable hazard areas such as unsighted bends. Lots of traffic accidents are a combination of factors, with additional circumstances that will make any crash orders of magnitude worse. It’s well worth looking not just at the vehicles and people involved, road conditions can change and sometimes subtly so - such as roadside signage, some years ago in the UK there was a series of roadside posters advertising lingerie with the strapline “Hello boys” with the image of a scantliy clad model demonstraing her ample assets whilst wearing the products of the lingerie company - it became legendary for a series of traffic accidents, especially on inner city roads where the poster was sited right above a bend. > **[Greece puts brakes on raunchy billboards](https://metro.co.uk/2007/05/11/greece-puts-brakes-on-raunchy-billboards-347057/)** > > Raunchy images of nude and scantily clad models are driving Greeks to distraction. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 4, 2020, 12:46pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/28 "2020-08-04T12:46:31Z")
> [@Dinsdale](#): > > This morning, a major highway in the Chcago area was shut down for several hours following [a 2-day accident with severe injuries](https://abc7chicago.com/chicago-traffic-crash-eisenhower-expressway-north-avenue/6350446/). > > We had to drive somewhere around 8 a.m. We neglected to check ahead of time, and found the entrance ramps blocked by police vehicles and traffic stationary. The radio said the entire 3 lanes of westbound traffic had been blocked for over 2 hrs as police “investigated.” > … I think the “investigation” part is mostly taking pictures of where the debris is, skidmarks, etc., before clearing it all away. Just the “clearing away” takes quite a while when you have a couple of large vehicles strewn across the road. And in the initial phase the “investigation” is checking to see if anyone can be saved, removing the injured and dead… My guess is they call the whole time “investigating” because that’s easier than actively telling the public exactly where they are in the process. But if the road was only closed for 2 hours, a lot of that time was removing the body and the debris. And that pretty much needs to happen before the road can be opened. ---
**Author:** ![Banquet\_Bear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/banquet_bear/32/373_2.png) [@Banquet\_Bear](https://boards.straightdope.com/u/Banquet_Bear)\ **Post date:** [August 4, 2020, 12:51pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/29 "2020-08-04T12:51:26Z")
> [@Dinsdale](#): > > **You miss the point.** I was exceedingly minimally inconvenienced. Hundreds (if not thousands) more were far more inconvenienced - standing still on the expwy for hours. That adds up (in this pitworthy scum’s opinion.) …you are wrong. **We all get your point** , as you keep **repeating your point**. Of course people inconvenience “adds up.” But a calculus has been made. We generally consider the accident investigation to have priority over holding up traffic. If possible the police would generally try to mitigate that hold up, but that isn’t always possible. If that makes you unhappy, then the only real solution for you is to lobby for change in your community, gain a critical mass, and force a change to be made. However I don’t like your chances, because why would people **not** want the investigation to be done properly? As to what do police do when the investigate a car accident that information is readily available online. Like from [here](https://www.edmunds.com/car-safety/investigating-fatal-accidents.html). Or [here](https://www.jdsupra.com/legalnews/how-to-investigate-a-car-accident-25384/). Or [here](https://driving.ca/auto-news/news/how-it-works-crash-reconstruction). Or [here](https://www.claydugas.com/blog/2016/september/how-forensic-evidence-at-crash-and-accident-site/). Or [here](https://www.knrlegal.com/how-does-a-police-officer-investigate-a-car-crash/). Reading those cites should be enough to be able to figure out “what police do when they investigate a car accident”, and should be sufficient to answer your General Question. ---
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [August 4, 2020, 1:44pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/30 "2020-08-04T13:44:15Z")
> [@Monty](#): > > OP: Why the quotation marks around _investigate_ in the thread title? … Just wondering whether the word was an umbrella term that might include some activities other than what others generally understand it to mean. Banquet Bear not sure why my question(s) seem to exercise you. But you can certainly ignore my posts, as I can yours. ---
**Author:** ![Banquet\_Bear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/banquet_bear/32/373_2.png) [@Banquet\_Bear](https://boards.straightdope.com/u/Banquet_Bear)\ **Post date:** [August 4, 2020, 1:47pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/31 "2020-08-04T13:47:11Z")
> [@Dinsdale](#): > > Banquet Bear not sure why my question(s) seem to exercise you. But you can certainly ignore my posts, as I can yours. …we are in General Questions. Did my post not directly answer your question? Why would I ignore it? Do you need any more clarification? Do you now understand what police investigate in a car accident, or do you need more information? ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [August 4, 2020, 2:09pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/32 "2020-08-04T14:09:40Z")
> [@Dinsdale](#): > > Banquet Bear not sure why my question(s) seem to exercise you. But you can certainly ignore my posts, as I can yours. Putting the word _investigate_ in quotation marks very well may have been interpreted as saying the investigators were not doing their job and that the entire event is just a lark for the police officers involved. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 4, 2020, 2:10pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/33 "2020-08-04T14:10:21Z")
I think we can all agree that the best-case scenario is to not have accidents, right? So how can we decrease the number of accidents? Well, the vast majority of accidents are due to at least one driver driving irresponsibly. So we want to discourage people from driving irresponsibly. How do we do that? We have laws against various sorts of irresponsible driving, and punish people who violate those laws, to give them an incentive to be responsible. But that only works if we know who’s driving irresponsibly, so we can punish the right people. That’s easy when a police officer happens to witness the irresponsible driving, like when they give you a speeding ticket. But now, what if there is an accident? We know that someone was irresponsible, but we don’t know who. In order to punish the irresponsible folks, to discourage future accidents, we need to investigate. ---
**Author:** ![needscoffee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/needscoffee/32/1076_2.png) [@needscoffee](https://boards.straightdope.com/u/needscoffee)\ **Post date:** [August 5, 2020, 2:03am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/34 "2020-08-05T02:03:40Z")
> [@Dinsdale](#): > > My suspicion is that this is an instance in which someone came up with a standard procedure to be followed in each and every instance, with no consideration of specific circumstances. Which is how bureaucracies often work, but not IMO always desireable. The reason for standard procedures (if indeed they’re being used here) is because they don’t always know what’s going to be important until later, after it’s been documented (or not). Also, it’s not surprising that investigating crimes takes precedence over the inconveniencing of commuters. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [August 5, 2020, 4:23am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/35 "2020-08-05T04:23:16Z")
> > Well, the vast majority of accidents are due to at least one driver driving irresponsibly. This was my thought too. Whatever happened, whoever is at fault, there is likely some traffic law broken at minimum. The documentation of the scene - in proportion to the severity of the accident outcome - is necessary to establish the likelihood of which laws were broken. OK, DUI is easily proved without stopping traffic. (If done right, at the proper time). But if the person denies they fell asleep or says they were braking or that the other car jammed on the brakes in front of them… or that their tire blew so they lost control, or that the traffic light was not lit up red… all possibilities need to be documented. Start and location of skid marks (or lack) indicates when the driver tried to stop. That’s something that cannot be verified six months later when it all goes to court. It has to be documented at the time. And so on. So it’s not to provide ammunition to civil suits, it’s to provide ammunition (or exonerate) those who may be liable for traffic or criminal charges. As is usual in the system, what the criminal courts say about an action usually determines what civil courts will do. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [August 5, 2020, 3:58pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/36 "2020-08-05T15:58:30Z")
And, every once in a while, the investigation of a vehicle wreck leads to something bigger still. The OP, like myself, lives in the Chicago area, and he may remember that, [in 1994, six members of a Chicago-area family were killed in a fiery wreck in Milwaukee](https://abc7chicago.com/willis-family-crash-george-ryan-anniversary/5683148/). The investigation of that wreck (which was caused by a part that fell off a truck) led to a federal investigation ([Operation Safe Road](https://www.chicagotribune.com/news/ct-xpm-2003-12-18-0312180299-story.html)), which uncovered widespread corruption in the Illinois Secretary of State office (which operates motor vehicle licensing in the state), and in turn led to [the conviction and imprisonment of former Illinois governor, George Ryan](https://en.wikipedia.org/wiki/George_Ryan#Scandals,_trial,_and_conviction). ---
**Author:** ![Kron](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kron/32/12444_2.png) [@Kron](https://boards.straightdope.com/u/Kron)\ **Post date:** [August 5, 2020, 4:08pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/37 "2020-08-05T16:08:59Z")
> [@Loach](#): > > A routine accident with no or minor injuries just needs a good eyeballing. > > A collision involving death, serious bodily injury and/or criminal charges (not just DWI) involve a lot more. Our fatal accident team (of whom I used to be one) do a full scale diagram of the scene rather than a not to scale sketch. The scale diagram is done by using laser mapping for precise measurements of the entire scene. It takes a long time. If it’s a large scene it takes even longer. > > > [@jnglmassiv](#): > > > > Don’t think for a second that this isn’t milked by police. Investigating a traffic accident is a great way to spend a shift. > > It is actually a really shitty way to spend a shift. They get cleared as soon as possible. Yeah, back in my firefighter days, I can’t think of anything that sucked more than spending a good portion of a day at an accident scene… I can’t imagine the police officers felt any different. ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [August 6, 2020, 1:59am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/38 "2020-08-06T01:59:12Z")
I can’t speak for police officers. But I’d imagine that they first check to see if anyone needs medical attention, is trapped or has died (after making sure they can do this safely). Then they need to determine if there are things requiring attention: involved power lines, spilled fluids or cargo, debris, fires, spilled chemicals, damaged infrastructure. Things like weather conditions - fog, ice patches, snow, etc. could change quickly and so would be better documented early. The police would interview people to learn what happened, estimate travelling speeds, look for skid marks and evidence, take pictures of damage, document signage and traffic lights. They’d have to keep people away while performing these duties. It sounds like everything needs to be documented to scale and to a high standard when there is serious damage, injuries or deaths. It would not be hard to envision hundreds of thousands dollars worth of damage to cars and infrastructure with complex insurance demands. And injuries and deaths could reach considerable amounts of litigation. Accidents happen due to weather, animals, alcohol, drugs, diabetes, heart attacks, excessive speed for road conditions, all sorts of things. I’m sure there are more enjoyable things to do. Things need to be done and safe before letting people drive through. There are usually alternate routes. My one pet peeve is that when a highway is closed, there could be signage or information early enough to easily allow an alternate route to be taken — 10km away — although I get that there are higher priorities than the merely inconvenienced. ---
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [August 6, 2020, 2:20am UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/39 "2020-08-06T02:20:50Z")
Accidents on interstates are typically handled by state police. All cops can do certain basic things like patrol but only certain cops can do more specialized tasks, whether that be SWAT/CERT/ESU, K9, certified to perform DUI testing &/or accident investigation. The accident investigators need to be summoned to & arrive at the scene; then possibly wait for EMS/Fire to clear the scene. You’ll need add’l PD or DOT workers to both close the road & force everyone off at an exit/not allow people on at upstream entrance & possibly add’l police at the bottom of the ramp to pull traffic. In short it’s not one cop up there thinking “siesta time”. The sargent/lieutenant is probably going to get on the investigating team if they’re taking too long as there’s a lot of manpower tied up & if that manpower is from DOT & they’re taking too long, you can bet a DOT supervisor is going to call the sargent/lieutenant & say how much longer, my guys aren’t plowing/mowing/fixing potholes because they’re sitting in trucks to close the highway. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [August 6, 2020, 3:36pm UTC](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172/40 "2020-08-06T15:36:16Z")
People (and governments) vastly overestimate the value of their time while driving, as if they’re on the clock 24/7 and any extra time spent behind the wheel represents actual money being sucked out of their wallet. This has allowed for ridiculous cost/benefit analyses that justify multi-million or even billion dollar projects that save 30 seconds of driving because “30 seconds times hundreds of thousands of people per day adds up.” Trust me, nobody’s deserving of “a check for a couple hundred bucks” after sitting in a traffic jam for a few hours. This discussion also exposes two very opposite viewpoints on roads and driving in general. There’s some people who feel that any road deaths are both preventable and unacceptable (vision zero), and others who think that deaths and injuries are perfectly acceptable in the name of so-called “happy motoring.” These two groups tend to talk past one another and try to justify policies that the other person thinks are ridiculous or reprehensible. I’m seeing this dichotomy in the previous replies. “A person died FFS!” versus “Thousands of people were inconvenienced needlessly!” If you want to take those arguments to their logical conclusion, then a typical person’s lifetime economic value is roughly $10 million. Investigating their death in a car crash for five hours, blocking 10,000 other motorists, who are all “on the clock” at $20/hour would still only be $1 million. That’s a rather cold and detached way to look at it, but so it goes. One other logistical thing is that if the crash involves a large semi tractor trailer, those can be a bitch to move. If it’s damaged to the point it can’t move under its own power anymore, or if it’s stuck in the mud, or overturned, it takes some pretty specialized hefty equipment to handle that. You can’t just call Joe Blow’s Towing and have a truck there in 20 minutes. Even if the big heavy-duty tow truck is available, they may still need a crane, or at the very least a lot of steel cable rigging that takes time to set up properly, on top of all the other investigative operations already discussed. [Previous page](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172.md?page=1) [Next page](https://boards.straightdope.com/t/what-do-police-investigate-in-a-car-accident/917172.md?page=3)