Highways officers and South Yorkshire Police have answered the question on all Sheffield drivers' lips.
The M1 was transformed into a 'smart motorway' between junction 32 and 35A in March last year but there has been much debate about whether the newly-installed speed cameras were active when no temporary speed limits were in place.
Overhead gantries are used to apply temporary speed limits and lane closures when there are incidents on the carriageway and drivers will be flashed for breaking the limits.
And now, for the first time, South Yorkshire Police and South Yorkshire Safety Camera Partnership, who are in charge of speeding fines across the county, have said they have the power to use the cameras 'when it is deemed appropriate'.
READ MORE: Taking to the road to find out more about how Yorkshire's 'smart motorways' work
A spokeswoman said: "South Yorkshire Police and South Yorkshire Safety Camera Partnership have the capability to enforce the posted or national speed limit on all roads within South Yorkshire including the motorway network.
"Such enforcement will take place when it is deemed appropriate and proportionate to do so in order to prevent or reduce road collisions and casualties and protect all road users."