http://www.pushhogg.com/energy-saving-lamps-disadvantages/
Should we conserve energy by turning off our street lamps between the hours of say 1am and 5am?
Think of the energy that would be saved.
Advantages include a financial saving (although this probably will not show in our council tax bills!)
Astronomers will have dark skies.
Environmental advantages by saving energy.
Perhaps a disadvantage would be personal safety to anyone walking about in the early morning hours?
Rapists, robbers! Crikey! where do you people live?
yes, some areas may have a problem with burglaries, but isn’t that the problem of the home owner not keeping security up to date?
Rapists….not where I live.
As for motorists not seeing fallen trees or obstacles. OMG! Do you drive with your headlights turned off? 
Not every road is lit by streetlights.
There is a simple answer. Turn off every other light, or, better still turn off two, have one on, turn off two etc.
Initially there would be a cost of putting in two wiring circuits but this would eventually recoup itself.
That said the saving would be insignificantly small in that that is achievable by improvements in efficiency of generation, lighting and transmission systems.
Whilst we are energy hungry and present methods of generation are polluting – the answers are out there to turn it all around. Changing from a coal fired generator to a gas one would halve the pollution and changing to nuclear, or alternative power sources would wipe it out.
The answers you have received though suggest a further possibility – getting people to get a real appreciation of the risks of daily life! If people would only look beyond their irrational fear and quantify the real dangers they would see that the risks of rape, burglary and murder are tiny. They are far more likely to die in an accident in the home. So perhaps they would gain enough confidence to switch off some lights themselves!!!
Smashed halogen light bulb still works