How do they close the road and control traffic before they begin putting up the “Road Closed” signs?

Question

How do they close the road and control traffic before they begin putting up the “Road Closed” signs?

In: 8

Answer 1

Normal road, put sign up and start diggin

Highway, those arrow trucks or just 3 cop cars enter a few ramps in advance at noght, get to the needed speed and let everybody behind them slow down and exkt the highway. Then close all ramps and start diggin

… So just an awfull lot of diggin