Hard to gauge speeds at night. Inattention, illusion, or visual deficit?

October 16, 2006 6:12 AM

Is there any sort of recognised optical illusion or visual deficit that can make it hard to realize that a vehicle is stationary?

A friend of mine is a lawyer. S/he is looking for a lead that may save someone from going to jail.

My friend's client was driving his truck in the right lane of an elevated road at night. A car had stopped in the lane ahead because the driver's passenger felt sick. There was no stopping lane, nothing was to the right of the car but a guardrail. Three other cars had stopped behind the first car. My friend's client struck the last car, killing the people inside.

I've noticed that it can be hard to gauge speeds at night. In this case the road was lit but there were no visible trees or houses. The driver will have seen the road surface, the guard rail at the side of the road, the poles supporting the street lights, cars travelling in each direction and the stationary cars. Is there any reasonable explanation other than inattention for him not realizing that the cars were stationary? He doesn't recall the moments before the crash.

If it makes any difference, I'm not the lawyer or the client, and I don't know the client.

posted by anonymous to Law & Government (17 answers total)

I was involved in a similar accident, though without such a terrible outcome. I was on a moderately trafficed highway on a clear day in the center lane. There was a car stopped up ahead in that lane but when I first noticed it I just thought it was going slow so I slowed down a bit too. It took another second or so for me to realize it was standing still and since there were cars on either side of me I couldn't change lanes fast enough. I slammed on the brakes and rammed the standing car, then got hit by the car behind me. To this day I can't figure out why I didn't realize that the car was standing still until it was too late. Of course if the car had its blinkers or brake lights on that would have helped.
posted by EiderDuck at 6:37 AM on October 16, 2006

Wet pavement would be the #1 problem, after inattention. Wet windshield may also contribute.

Also, 1 eye substatially worse than the other imparis depth perception (when not corrected with lenses, of course).

Excessively bright break lights on the stopped car may cause some drivers to look away. This would be more the case where there are no streetlights, which reduce the blinding effects of car lights in the dark.
posted by Goofyy at 6:45 AM on October 16, 2006

A sense of speed is gauged by relative movement of objects in relation to others. If there's an argument to be made that all the driver didn't have a frame of reference for the speed of the cars ahead (ie only lights ahead) and the perspective was such that the expected movement of taillights was very close to eye level, it could be argued that it was hard for the driver to easily determine if the cars were moving. Rain would cause some diffraction of the lights in the windshield, making it hard to judge absolute size and reducing the ability to judge their increasing size as they were approached.

I'm no lawyer and I know this doesn't need to be said for your sake, but I'm guessing the hard bit would be to provide a compelling enough argument that a reduction in speed as a result of doubt about the cars' movement wasn't the most prescient thing to do (ie no reason to think that the cars weren't moving, and slowing down would put him/herself in danger in a no-stopping lane).
posted by jimmythefish at 7:14 AM on October 16, 2006

At night, you are often basing distance judgements solely on the car's lights. If they are moving apart, you are getting closer, and vice versa. This method can fail if you aren't looking at the right lights.
posted by smackfu at 7:21 AM on October 16, 2006

As noted above, blindness or visual impairment (partial or total) in one eye can cause severe depth perception problems. If the client had that sort of problem, however, it's highly unlikely they'd have been granted a normal driver's license.

Also, if it was at night, there may have been a lack of ambient lighting. Does the client ingest enough Vitamin E to have good night vision? A deficit in that regard could have led to this occurrence...
posted by limeonaire at 7:33 AM on October 16, 2006

You may be able to combine some of the information on visualexpert.com about driving in fog with night vision.

"We see objects, not based on their absolute brightness or darkness, but on their difference between the object brightness and background. Fog lowers contrast substantially, causing objects to become fainter and less distinct."

"Lower light level changes the balance in contradictory demands of light sensitivity on the one hand and contrast sensitivity on the other."
posted by FreezBoy at 8:33 AM on October 16, 2006

Something very similar also happened to me at night but not with your friend's client's horrible result. My problem was, the driver of the car I rear-ended didn't have his foot on the brake (instead, he'd set his emergency brake), so I didn't realize his car wasn't moving.
posted by Rash at 9:05 AM on October 16, 2006

... because his brake lights weren't on.
posted by Rash at 9:14 AM on October 16, 2006

I sometimes experience an odd kind of optical illusion while driving. I don't know whether it's unique to me; I didn't find any references to it with a quick search, but maybe someone else will have better luck.

It happens when my attention is fixed on the car ahead of me. Rather than experiencing a smooth, continual change in the distance between my car and the one in front, I experience the distance changing in a series of freeze-frames. So if I'm gaining on the car, I see it kind of flashing larger and larger, rather than steadily growing. This can definitely make it hard to tell how quickly I am gaining on it, as well as whether or not it is moving at all.
posted by gorillawarfare at 10:00 AM on October 16, 2006

Blindness or visual impairment (partial or total) in one eye can cause severe depth perception problems. If the client had that sort of problem, however, it's highly unlikely they'd have been granted a normal driver's license.

This doesn't fit my experience in the USA. I'm blind in one eye, and I can drive as well as anyone else; I obviously have to be aware of my limitations, but it isn't a crippling problem. Last time I took the eye test at the DMV, I told them the situation, they accepted it, and that was that -- no restrictions on my license or anything.

On the other hand, if I needed a license to play tennis, I'd have serious problems...
posted by xil at 10:00 AM on October 16, 2006

Rash's post could be a possibility but it would be hard to prove/determine if the last car's brake lights were working or in use. Ideally you should be able to see brake lights on cars several cars ahead of you unless you are in a low-rider vehicle like a vette.
posted by JJ86 at 12:09 PM on October 16, 2006

I have nearly had accidents when a driver puts the car in park instead of putting on the brakes or just turning on the hazards, even at very slow speeds. If the rear lights were not at full brightness, I think that any number of road safety expert witnesses could provide the kind of testimony your friend is looking for. Expert witnessing is pretty good money, so finding one shouldn't be too hard.
posted by Lyn Never at 12:17 PM on October 16, 2006

During the daytime, you have several cues that a vehicle has stopped: brake lights, apparent vehichle size, or the clustering of cars, visible even if the brake lights are obscured.

At night, all you have are the brake lights and their angular separation. The brake lights are not as distinct from running lights — they may just be another shade of red. So more attention is required.

But every driving manual or guide says you have to pay more attention at night, and if you are sleepy, you should stop driving. To me, this says that there is no excuse for inattention. If you have some syndrome that makes it hard for you to tell when you're catching up to an immobile object at night, you should have become aware of it over your 20-50 years of driving experience and taken action accordingly.

Guilty, guilty, guilty!

I have some bias on this issue because a friend of mine was killed in just such a situation over Labor Day weekend. Flat tire in the carpool lane at 5AM.
posted by Araucaria at 1:02 PM on October 16, 2006

I think the question I'd ask is: How is driving with palinopsia or micropsia or macropsia or a visual migraine any less criminally negligent than plowing into a stopped car because you weren't looking where you were going?
posted by ikkyu2 at 1:22 PM on October 16, 2006

First, I'm sorry that happenned to your friend. My heart goes to the familly and friends of the victims.

I though it was common knowledge that you should get out of your car if you are immobilized the middle of the road. At highway speeds, it's almost impossible to tell the difference between a car at 40km/h and a stopped car.

A friend-of-a-friend had the same crash, and the same reaction: see the troubled car ahead, starts slowing down, realize in horror that that car is actually stopped, smash the breaks and crash at medium-slow speed.
posted by gmarceau at 2:19 PM on October 16, 2006

It's tunnel-vision. Yes, there were things he could have seen that would have indicated that the car ahead was stopped, but most people kind of tunnel in on the car ahead of them. Perception of speed coming straight at or away from you requires processing the increase in the size of the object, which for a car is going to be minimal. Couple that with the known phenomenon of people seeing what they expect to see(a car slowing, rather than stopped), and that explains the illusion. It's especially hard in low-light situations. There's probably some research somewhere regarding our perception of speeds of items coming straight towards the observer versus crossing the field of vision.
posted by Mr. Gunn at 5:24 PM on October 16, 2006

This may be a stretch but...

In a neurobiology class we discussed vision and perception,
lots of interesting research there...of note possibly...is (pretty shady memories here) the physiological reasons that the human eye can track blinking lights with greater accuracy than solid lights. This is apparently the reason airplane lights generally blink intermittently instead of always on.

I forget the name of the effect, but a little research would find it quickly if you thought the idea worthwhile.
posted by skinnydipp at 1:46 AM on October 17, 2006