You've got the wrong crew foremen.
Here's how I'd work it, but it will take years to fully implement this:
Overall you need to inculcate a work ethic in them -- a desire to do a good job every time.
1. As any given crew gets better the supervisor visits less often.
2. Crews that need visiting less often get a bonus on their paycheck. After all they have taken less time.
3. The foreman turns in a sheet each day of the route and time at each stop. If you are suspicious of a foreman, you pull the GPS log off the vehicle.
4. From the log you get average times for a particular contract.
5. From the log you also get abnormal times. Abnormal times mean one of two things: * The contract was underbid. * Or these guys are slacking off.
6. Jobs that raise flags in #1 get a visit from the supervisor.
7. If you want to make sure, swap a different crew onto that job for a few weeks.
8. Overall, crews are paid a base rate plus a percentage of the contract. This has to be adjusted carefully. If the contract part is too big a fraction, they tend to rush the job and do badly. If the contract part is too small, they goof off.
But judging quality is a lot easier to document than how they spent their time. However, a crummy job may require some fast talking with the land owner to fill in, so bad jobs shouldn't come up too often.
Overall you want to create win-win situations. The original poster is working himself into a management vs employee war. This seldom ends well. You end up with employees who will do the minimum possible work. Instead figure out a method that it's to everyone's interest to pull the same way.
As to personal freedoms:
1. Starting time should be fixed at least in a given season. There is merit in starting your workday early in summer to keep out of the heat. There can also be merit in having some flexibility -- e.g. if you have a bunch of single employees who need to get their kids off to school, make a crew for them, allow them to start late.
Ideally if you have a salting route, then move the whole day to the time the guys need to start. If there is extra time becuase of no-snow, this is time to work on maintenance, other projects, or let them book off early.
Variable start times kill efficiency. On days you start early, people are half asleep the first hour or two. On days to start late, it's little better. If you are going to be flexible, be so at the end of the day.
(I used to run canoe expeditions with teens. I found that trips where we started at the same time every day invariable got more miles in a week than a trip that had 'easy days' and 'push days' So I got them up soon after sunrise, we got on the water 90 minutes later, usually by 6:30. The variable part was at the other end of the day. If we hit a cool waterfall or rapid at 3 in the afternoon, we may stop. If we in a chain of portages amid the black flies, we may just keep slogging on, as we weren't much more miserable moving than stopped.)
I also found working with teens, that having mid morning and mid afternoon breaks WITH FOOD made a huge difference. I think this is true for any physical job. Feed people so their blood sugar doesn't drop and they don't get owly. Schedule it into their day, and it should become part of the foreman's time sheet. Foremen should note guys who didn't bring stuff for breaks, watch them for slow downs before lunch and quitting time.