Generally yes.
they can have there fines doubled
Yes, it has legal meaning and is legal to be there. It means that there is construction ahead so you should drive carefully and go slowly. It also means that there may be workers and is sometimes accompanied by a sign that says "Fines doubled when workers present" or something of that sort. I hope that answers your question, since you were unclear in your wording.
you must deduct 10 mph from the posted speed limit at all times..... WRONG Double Fine Zones Due to increased collision-related injuries and fatalities certain roads are designated as "Safety Enhanced- Double Fine Zones." Fines for violations are doubled in these zones and also in highway construction or maintenance zones when workers are present. (CVC §42010)
Traffic violation fines are generally doubled when the infraction occurs within or traveling through a construction zone.
In many states this can double your normal fine for speeding. In other states there may be signs that post the minimum fine you will get for speeding in a construction zone.
In Florida, fines are doubled for speeding in a construction or school zone. Fines vary by county in Florida. You should check with your county clerk in order to assess your fine.
no
Fines are normally Double for violating the speed limit in a construction zone.
Speeding fines are doubled when workers in a construction zone or children in a school zone are present. Not entirely correct as it depends on the State you are in. Ex. Alaska has a bill pending right now (April 2013) that would double the fines.
Speeding fines in some places double on holidays and in construction zones. They also tend to set up speed traps on certain weekends and holidays.
The spelling "fines" is the plural spelling of the noun fine (a monetary penalty).It is also a present tense verb (to fine). The similar verb is to find, conjugated as finds.