Work zone speed limit

In Pennsylvania:
In construction, maintenance, or utility short-term operations, a work zone speed limit up to 10 mph below the normal speed limit may be established without an engineering and traffic study if the work  zone speed limit is not less than 25 mph and is posted in accordance with Chapter 212. A reduction greater than 10 mph below the normal speed limit or below 25 mph on short-term operations or a reduction in speed on long-term operations may be permitted if an engineering and traffic study indicates conditions warrant. Conditions include traffic queues, erratic maneuvers, high accident rates, or undesirable working conditions that exist on the operation or have existed on similar construction, maintenance, or utility operations and indicate that additional safety measures will be necessary.

Speed reductions apply to any type of highway, i.e., a conventional highway, divided highway, freeway, etc.
Communication with motorists uses signs similar to the standard speed limit sign, but with a black-on-orange WORK  ZONE banner at the top of the regulatory sign.

For short-term operations, signs would only be in place while work is in progress, but some long-term projects will have signs in place day and night.

If signs are left up overnight but the reduced speed limit is not applicable, the signs will be covered.