Labor laws covering jobsite to jobsite travel pay?

I have been looking over the Labor laws online, looking for a certain issue, but cant seem to find a section nor paragraph covering this:

1) We are told to report to a usual job site ("the Shop") 30 minutes before official start of shift, leave our personal vehicles there, and get into a company van. If we don't get there in time, we are considered "Absent" and are sent home without pay.

2) That van takes us to a work site that is approx 25 minutes travel away.

3) IF traffic was not too bad we then punch in our time cards at this remote site at typical start of shift time.

--- if late then we dont get the full 8 hours pay that day- only getting paid from actual punch in to punch out.

4) At end of shift we punch out at the remote site at the typical end of shift time, and get back into the Van for return to "the shop".

---- sometimes traffic is so bad it takes a full hour to get back.

So, we come to work a half hour early, and sometimes don't get to our vehicles an hour late, without it being paid for that extra time.

I think this is unfair (and what if we get injured while riding in the work van off the clock?), and wrong/in violation of labor laws, but cant cite a reference to prove it.

Could someone provide a link to that paragraph/code, if it exists? Or if the above is standard business practices, and I am just expecting too much, then let me know if that is the case