Why don't you take down your traffic lights and hoardings as soon as you've finished a job?
Although it may appear that there is no-one working on the site, it doesn't mean the work has actually been completed.
Sometimes, for safety reasons, we have to allow one process to 'settle' before starting the next stage.
Even after the main work has been completed, we cannot reinstate the ground in one go - a temporary surface will be laid but this has to be given time to settle before the top layer (of concrete, asphalt etc) can, in turn, be laid and set.
Only when this full reinstatement has taken place is it safe for us to allow traffic to use the section of the road once more.