How Far Can You See When Driving at Night?

Low Beam PatternFreeways in British Columbia are governed by posted speed limits of up to 120 km/h and for the most part are only lit by a driver's headlights at night. The opposing lanes are fairly close together and require the use of low beam headlamps when other traffic approaches. When the highway is busy drivers are often forced to travel long distances on low beam. How safe is this at 120 km/h?

The average vehicle takes about 81 meters to slide to a wheels locked panic stop at 120 km/h. Some may stop a bit faster and more than a few will take longer, particularly pickup trucks and other larger vehicles. A driver who is alert and expecting problems will likely have about one second pass between identifying something on the road and actually getting the brakes applied. This means a further 33 meters of travel, bringing our total stopping distance to 114 meters.

Transport Canada says that the low beam lighting system of most vehicles allows a driver to see about 140 meters. It may seem further, but after that point most of the light is on the shoulder and the right ditch rather than on the lane ahead. This applies to both halogen headlights and the new gaseous discharge lamps.

The 26 meter distance between the end of the stopping distance and the end of the sight distance is travelled in less than a second. This is not a lot of time for a driver to react if they are not looking at the part of the roadway the obstruction is in, or are not completely alert and expecting to take action.

The gist of the calculation is that 120 km/h may not be a good night speed for drivers.

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Comments

Submitted by E-mail

Regarding the recent subject, Alberta vehicle equipment regs require low beams illuminate minimum 30 metres ahead (see below). I think the 140 metres in the article is unrealistic. 30 metres is completely inadequate. It's a difficult balance for illumination vs oncoming glare.

High and low beams

7(1) The headlamps on a motor vehicle, other than a moped, must comply with subsections (2), (3) and (4).

(2) A headlamp must have a low beam that can reveal a person or another vehicle that is at least 30 metres ahead.

(3) A headlamp must have a high beam

(a) that can reveal a person or another vehicle that is at least 100 metres ahead, and

(b) that does not shine in the eyes of an approaching driver.

Submitted by E-mail

Your recent comments on the 110 km/hr freeway speed limits and their impracticality (downright hazard!) at night are bang on.  I’ve never understood how it is that the highways design folks can justify having speed limits posted only for optimal conditions, or at least don’t take extra care in educating the driving public about the reality of what the speed limits are for.  There are far too many drivers who take the speed limit to be the speed at which traffic should be travelling on any given stretch of road – to the point where they react with aggression and frustration when they confront someone driving 80 kph at night through an area known for deer traffic/crossings, when the posted limit is 90 kph.  Driving between Grand Forks and Christina Lake at the posted speed limit at night is almost guaranteed to put you into far too close a proximity to a deer!  I don’t know how many times I’ve been hi-beam flashed, honked at and generally abused by other motorists, who see the speed limit and believe that it’s some sort of mandate to drive at that posted speed, in all conditions and at all times.

Other factors affect night vision

Modern cars with bright dash lights totally kill night vision.

Astronomers have know for years that dark adaptation is not affected much by red light, and is most affected by blue.

So what colour are most high-beam indicators?
You guessed it -- blue.

Dash lighting should be dim and red -- yet bright enough to read all necessary information.  When driving on dark highways I used a card to block direct light from the high-beam indicator, and this makes a noticeable difference which lasts until the first oncoming car is encountered.

Highway lighting should illuminate the target (usually the road) but NOT shine directly into the drivers eyes.
Newer full-cutoff fixtures are a huge help in this regard.

Age is also a big factor.  Diminishing night vision coupled with increased reaction time in older people needs to be taken into account.

Regards,
--BM
 

Great article

It highlights the "perspective" a driver should be aware of - getting to the destination intact.
Every driver should be able to estimate the risks in-front of them and apply their judgement accordingly.
Speed is always relative to conditions: visibility, road condition, driver's state of mind, road familiarity and car condition.

One thing to note, breaking should not be the default cure-all in cases where a collision is to be avoided, and lining yourself up to "panic brake" if anything out of the ordinary happens may not always be the best strategy.
I personally see nothing against going into the opposing lane or a shoulder if theres a snoozing driver barreling down my lane for a head-on collision.
It all comes down to paying utmost attention, and keeping physics in perspective (vectors of mass).
I have avoided just as many collisions by steering and accelerating out of the mass vector, as I did by promptly slowing down or stopping. (Great thing about moving mass - it can't change vectors with-out due notice, unless it's a UFO)

As far as the aggravated comment regarding the heat from the honking and high beaming tailgaters, I have to offer this perspective: We are all in-line for death, some sooner, some later, and who are you to protest when someone is trying to jump the line? (Please, go right ahead dear sir, is my perception)
Driving is not about enforcing your presence onto other road users, it's quite the opposite - getting out of everyone's way (whenever possible). So if you are not comfortable leaving the tailgater in the dust by switching into 2nd, revving to 9k and laughing at their insolence once at 200km/h, then kindly pull to the shoulder and smirk at their persistence in reaching their ultimate destination.

Having a distraught driver behind you, looking to pass in the on-coming lane as soon as a lonely on-coming car shows up is not good for either of yours' health. Keep it simple - keep away from objects, especially moving ones, double especially if they are controlled by humans.

P.S. Keep my comment in perspective - I don't recommend going 200km/h on any road, unless in Germany or a race track. That bit is about maintaining your driver confidence, and not getting mad at someone's seemingly unsafe practices. At any point you should be ready to face unreasonable humans, and your method of dealing with them should come from the perspective of your personal safety - as you don't need to "hold them back" you just HAVE to "get out of their way".

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