My understanding is that "Men Working' is a standard traffic control sign, like a stop sign or a yield sign. This standardization makes it easy for motorists to recognize a potentially hazardous condition. If the sign were to say something else, it would have to be very clear and iconically recognizable to be effective.
By taking them down, they amplify a hazard unless they have an equally effective replacement, like something that says "To the motoring public, we're improving the campus to give you a better driving experience and to beautify our lovely landscape. The project began on ..... etc etc.... (and by the way, be careful not to kill or maim anyone.). Warmest personal regards, the Campus Administration".