What is the rationale for the Bridge Laws?

Okay, I have just read thru all of this and need to do so again, but I have learned things I didn't know I didn't know so thanks for that everyone but I think from the pictures posted we have all missed the biggest question of all.... has @Long FLD ever driven a truck that was not at least partly blue?

 

Yes I have. Lol. My FLD and the truck I drove when I was in Hawaii.

 

Nice ride!

 

I didn’t read ever post, so forgive if I repeat.
The federal bridge formula was created in 1975( I was driving then) It is a federal law, every state enforced but it is almost impossible to be in violation with a 53’ trailer unless it has a super long slide. I don’t think there were many if any 48’ trailers at the time, they came out in the 80’s.

The king pin law is a state law, thus they can
Make the rules. 48 foot trailers are exempt from KP laws, that is why you can take a 48’ with a spread into California.

 

Here's another link about bridge formula.
Bridge Formula Weights- FHWA Freight Management and Operations

I have a 36' trailer with a sliding tandem, so I use this to understand how much weight I can haul with the axles at different positions. It's not enough to just take the measurement from the steer axle to the trailer axles for 5 axles, I also need to check the weight for 4 axles between drive axles and trailer axles. I can't just assume that I'm good for 34k on both of those axles. There is an exception to haul 34k on both axles if the spacing is 36 feet between tandems. Otherwise, I'm limited to somewhere between 55-65k depending on the distance I slide the tandems up.

 

Good thread.

 

What's the bridge law on this?

 

That long truck must be a handful to drive .. do you steer it like a bobcat?? That’s a interesting 4 axle setup though lol

 

Bridge laws have to do with actual bridges and the weight distribution across the axles on the bridges in conjunction with the design the truck/trailer.

It came out of the 1940's from the war, it was determined how to spread the weight across the bridge not to damage the bridge that the trucks were crossing with very heavy loads. The feds codified it so it applied across all the states due to issues in the 60's. During the war, there were a bunch of accidents with bridges collapsing caused by tight axle groupings on the trucks. One such accident killed the driver and two of the laborers who were on the truck in June of 1943, the truck was estimated at 109k and the entire truck, bridge and cargo went right into the river.

I have three heavy haul straight trucks which is 40 feet long, they don't need a long deck for the products they haul but I have to have axles spread out to take advantage of the axle capacity to meet the weight requirements of the products we haul. I have to be careful to make sure the up fitter will put the axles exactly as it was orders because three axles tight on the rear doesn't mean they can haul 60k, there has to be a spread to them to take advantage of the axle capacity.

 

The blue one