About the runaway truck ramps.....
They are very common in most every mountainous area in the US. They are indeed for use by trucks in the event of brake failure.
They are usually made of gravel or similar substance so that when a truck hits the ramp, it will literally partially sink the truck in an effort to slow and stop it. The steep angles also help slow the trucks as speeds on a runaway truck can be 100MPH or more easily! Once in, they can only be removed by tow trucks tied or anchored to tie points in the road nearby. There is no chance of sliding back down the hill once "captured". LOL
Air Brakes on BigRigs.....
Cars/pickups have mechanical brakes . When you press on the brake pedal, you move a cable that presses the brake shoes against the brake drum and slows the car.
On a big rig, you have to slow down a vehicle that can weigh 80,000 pounds. Thats 40 TONS! Plus, that means applying the brakes to 18 wheels. So, how is it done?
My truck (similar to others, but I will tell you as it applies to my truck) has 4 air tanks that hold air at 125 PSI (pounds per square inch). When I apply the brake pedal, it blows air into all the wheels/brakes on the tractor/truck AND the trailer. This behaves the same as the mechanical cable on your car. It presses the brake shoes against the brake drums all at the same time.
Big Rigs have TWO complete air systems. One is a service line, the other is a duplicate EMERGENCY air line. If one fails, there is a backup. That is why you see two air hoses connected to the trailer from the tractor. The other line you see is the electrical lines for lights, etc.
Ok, now mountain driving......
The basic rule is "Use the same gear to go DOWN the mountain as you used to CLIMB it". In other words, when you climb a mountain, the speed/gear we use depends on how steep, how long the mountain is, and what we weigh. Some mountains I have had to use 4th gear because I could not climb faster than 25 MPH!
Going downhill, you HAVE TO PULL the trailer down with you. That means you have to pick a speed/gear that is slow enough for you to keep pulling the trailer behind you as you go down. The trailer always weighs alot more than the tractor. If you go down too fast, the momentum and weight of the trailer will end up PUSHING the tractor down the hill. That is the fastest and easiest way to lose control in a heartbeat. The trailer will begin to come around and actually try to pass up the tractor and that is what is called "Jack knifing". I have seen many tractors that were completely runover and destroyed because the trailer actually ran over the truck!
If you are going down the hill faster than you want (you gain speed) then you brake semi-hard for a few seconds. Usually long enough to bring yourself down 5 MPH slower. If you stay on the brakes, they will heat up and catch fire. I have seen quite a few trucks at the bottom of the hill with trailer tires on fire or at least smoking horribly. Using the brakes too much going downhill will heat them up and the hotter they get, they begin to "fade" and fail. Once you lose them, it is too late. Once brake shoes heat up to the point they fail, (assuming you dont catch fire) they are destroyed.
My trainer years ago explained it to me this way: "You can go down a hill 100,000 times too slow, but only ONCE too fast". Makes total sense to me.
The other concern about mountain driving.....most mountains have sharp turns in them usually on the downhill side. You hit that turn too fast, and you flip the trailer into a roll over. Done deal. If you want to see what happens when a truck takes a turn too fast down a mountain, go here:http://www.gofastvideo.com/video/1854/Donner-Pass-Rollover-plus-after-the-fact-pictures# Warning!!! It is not easy to watch (for me anyway). IT IS NOT MY VIDEO...but another trucker captured it. The driver had his truck license just 9 days!
Once you start down the mountain, if you are not in the RIGHT gear.....(according to speed, etc) you will not have a chance to change gears midway. The truck will be moving too fast, and you will never get it back into gear.
Best, 100% chance to not have brake failure? Be dang sure you choose the right gear, and the right speed, even if that means you have to "crawl". LOL Better to get there slower than anybody else than to get there faster but not survive!
They are very common in most every mountainous area in the US. They are indeed for use by trucks in the event of brake failure.
They are usually made of gravel or similar substance so that when a truck hits the ramp, it will literally partially sink the truck in an effort to slow and stop it. The steep angles also help slow the trucks as speeds on a runaway truck can be 100MPH or more easily! Once in, they can only be removed by tow trucks tied or anchored to tie points in the road nearby. There is no chance of sliding back down the hill once "captured". LOL
Air Brakes on BigRigs.....
Cars/pickups have mechanical brakes . When you press on the brake pedal, you move a cable that presses the brake shoes against the brake drum and slows the car.
On a big rig, you have to slow down a vehicle that can weigh 80,000 pounds. Thats 40 TONS! Plus, that means applying the brakes to 18 wheels. So, how is it done?
My truck (similar to others, but I will tell you as it applies to my truck) has 4 air tanks that hold air at 125 PSI (pounds per square inch). When I apply the brake pedal, it blows air into all the wheels/brakes on the tractor/truck AND the trailer. This behaves the same as the mechanical cable on your car. It presses the brake shoes against the brake drums all at the same time.
Big Rigs have TWO complete air systems. One is a service line, the other is a duplicate EMERGENCY air line. If one fails, there is a backup. That is why you see two air hoses connected to the trailer from the tractor. The other line you see is the electrical lines for lights, etc.
Ok, now mountain driving......
The basic rule is "Use the same gear to go DOWN the mountain as you used to CLIMB it". In other words, when you climb a mountain, the speed/gear we use depends on how steep, how long the mountain is, and what we weigh. Some mountains I have had to use 4th gear because I could not climb faster than 25 MPH!
Going downhill, you HAVE TO PULL the trailer down with you. That means you have to pick a speed/gear that is slow enough for you to keep pulling the trailer behind you as you go down. The trailer always weighs alot more than the tractor. If you go down too fast, the momentum and weight of the trailer will end up PUSHING the tractor down the hill. That is the fastest and easiest way to lose control in a heartbeat. The trailer will begin to come around and actually try to pass up the tractor and that is what is called "Jack knifing". I have seen many tractors that were completely runover and destroyed because the trailer actually ran over the truck!
If you are going down the hill faster than you want (you gain speed) then you brake semi-hard for a few seconds. Usually long enough to bring yourself down 5 MPH slower. If you stay on the brakes, they will heat up and catch fire. I have seen quite a few trucks at the bottom of the hill with trailer tires on fire or at least smoking horribly. Using the brakes too much going downhill will heat them up and the hotter they get, they begin to "fade" and fail. Once you lose them, it is too late. Once brake shoes heat up to the point they fail, (assuming you dont catch fire) they are destroyed.
My trainer years ago explained it to me this way: "You can go down a hill 100,000 times too slow, but only ONCE too fast". Makes total sense to me.
The other concern about mountain driving.....most mountains have sharp turns in them usually on the downhill side. You hit that turn too fast, and you flip the trailer into a roll over. Done deal. If you want to see what happens when a truck takes a turn too fast down a mountain, go here:http://www.gofastvideo.com/video/1854/Donner-Pass-Rollover-plus-after-the-fact-pictures# Warning!!! It is not easy to watch (for me anyway). IT IS NOT MY VIDEO...but another trucker captured it. The driver had his truck license just 9 days!
Once you start down the mountain, if you are not in the RIGHT gear.....(according to speed, etc) you will not have a chance to change gears midway. The truck will be moving too fast, and you will never get it back into gear.
Best, 100% chance to not have brake failure? Be dang sure you choose the right gear, and the right speed, even if that means you have to "crawl". LOL Better to get there slower than anybody else than to get there faster but not survive!
