Help-what is stopping distance on gravel roads

[mdbarb]

I can't find the answer so I'm turning to my TBN team.
I have been searching the net to find facts on what the stoppping distance would be for a vehicle traveling various speeds on a gravel road.
Can anyone point me to a page with such info?
Thanks in advance

 

[beenthere]

Re: stopping distance on gravel roads

First, I don't have a page with such info, but I grew up (i.e. I put in some time) driving on gravel roads in Iowa. It will depend on many factors and conditions of the gravel, the kind of gravel, when it was last graded, and what the recent rains (weather) and traffic conditions have been. Sometimes gravel roads would have a solid base, and be near to concrete. Other times there would be loose gravel and be like driving on marbles. I couldn't possibly think that all these conditions could be controlled well enough to come up with a "table" of stopping distances at various speeds, let alone trying to describe the vehicle (weight, tires, speed, etc.) that would also have to be controlled. I will be interested in what is available from the TBN folk.

 

[mdbarb]

Re: stopping distance on gravel roads

I have been able to find charts showing stoppping distance at different speeds on an ashpalt or concrete surface but gravel would be quite different. I just need a legitimate reference - I'm sure the studies have been done and even more sure the TBN crew knows about it

 

[beenthere]

Re: stopping distance on gravel roads

What might you be using this information for? Sounds interesting.

 

[Turfman]

Speed equals 5.5 times the square root of the distance of the skid (all wheels locked) times the coefficient of friction for the road surface plus or minus any grade.
S=5.5 * Square Root of (D*(F±f)) (Sorry about this formula, I typed it in Word and copied it and lost the radical sign that is the the righ of the 5.5.)

Therefore, (stopping) distance equals the speed squared divided by 30 times the coefficient of friction for the road surface plus or minus any grade.
D=S^/(30*(F±f))

The coefficient of friction for gravel is between .40 and .55, slightly better than snow. All this depends on all wheels locking for an all wheel skid. Braking, non-locked wheels will have a shorter stopping distance. The smaller the number on the coefficient the slicker the surface and the longer the stopping distance.

 

[RanchMan]

Turfman -

<font color=blue>The coefficient of friction for gravel is between .40 and .55, slightly better than snow</font color=blue>

I'm no mathematician, but with a little speed on a gravel road, I have to concur - it can get pretty "slick"!

 

[Anonymous Poster]

Usually, about 2 feet more than the distance to the back of the stopped tractor towing 3 full grain wagons.
Seriously, the answer ought to be in here someplace;

www.catair.net/carsearch.asp?stage=1

 

[Egon]

Seriously, the answer ought to be in here someplace;
Don't think so!!
Infinite variables in infinite combinations make for infinite solutions.
Love driving a rear wheel drive on a well graded, smooth, windy gravel road and steering with the accelerator

Franz; you have put forth the best answer yet.

Egon

 

[n6ckv]

Depends on the gravel. On most of the major highways that cross the mountians out west there are gravel traps to catch run away trucks (the ones that have lost their breaks). The traps deap gravel pits with some very solid tie downs for the tow trucks to use when removing a truck from the trap. The breaking distance is less than 50 feet.

carl

 

[Wingnut]

The one's I've seen in the mountains in Canada, Carl ... may be gravel or may be sand ... and depend as much on grade as they do depth of the "fill".
But you're right, the drag from the fill stops the trucks pretty quickly in those "brakeaway lanes".

"braking distance on gravel" - if you have to ask, prepare for impact!

pete (who spent much of his life living on gravel roads and was once accused of being totally insane when pulling his tent trailer with a Goldwing on a gravel road at "speed" (guys couldn't catch up in a pick-up))