Working hours for projects are usually determined at the time the construction plans are designed.
Design engineers consider the type of work, environmental factors and cost.
Some projects have certain phases which can be required to be done at night while other phases may be designed for strictly day work. Night work also lowers productivity due to having to work under limited lighting conditions and can extend the time and cost of a project. Major pavement resurfacing, however, is often performed during the night. Nighttime can be hazardous to workers and drivers because traffic is lighter, allowing motorists to travel faster through work zones. Less congestion may sound good, but slower traffic presents less of hazard.