What are performance requirements for heavy (commercial) trucks? [closed]

Question

As far as I understand it, DoT regulates heavy trucks on U.S. roads. But I've searched and inquired and I can't find any specific performance requirements that a truck must satisfy to be road legal. I suspect I'm just missing something. Examples I would assume would be regulated, but for which I can't find any indication they are:

1. Is minimum braking performance specified? E.g., at gross weight, must a truck be able to stop from a certain speed in a certain distance on a specified surface?

2. Is there a minimum acceleration requirement? E.g., can I pull an otherwise legal 80,000 pound trailer with a 100ft-lb tractor?

3. Is there a maximum weight per tire contact patch?

4. Is there a minimum turning radius?

5. Is there a minimum turning speed? I.e., a limit on how top-heavy a load can be?

Any indications as to how (and which) performance requirements are specified, tested, and enforced would be interesting!

Answer 1

Great question.

This got me looking searching Google for answers, and I'm surprised there doesn't seem to be a simple integrated answer anywhere. Two links of interest.

1) Wiki - trucks The references at the bottom of that article are pretty useful.

2) Iowa State Conference on Performance based standards, 1996. Its old, but has the right thought process.

I've enjoyed 30 minutes of searching, but nothing jumps out at me.

I will say, there seems to be a definite dividing line at specifications involving safety, emissions, and the protection of roadways, bridges and infrastructure. You can find stuff on emissions and braking pretty easily. Ditto for widths, lengths and axle loading, with regards to protecting roadways.

I didn't find anything on performance requirements. My suspicion (based on 30 years of experience as an automotive design engineer and manager) is that market pressures will drive the requirements here. Purchasers of trucks want low price, good performance, good fuel economy, low maintanance requirements and high durability (not necessarily in that order) The manufacturer does their best at their compromise, and the buyers reward those characteristics that best meet their needs (and wallet).

The one that really got me thinking was the power requirement. What really matters to fleet buyers is cost / ton of cargo / mile. Don't forget you have to pay drivers too. My guess here is bigger is better (i.e. cost optimal), but that's just a guess. Unfortunately, I never worked in the heavy truck arena.