How important is street light on roads?

• Provide safety for pedestrian and driver
• Improve visibility for above both
• Reduce accident rate and may save life 
• Reduce maintenance cost
• Also add beauty to road

Street lights, if designed well, can make any street look better and more beautiful than without it. Also, it makes pedestrians more secure to walk in the street, that they won't be attacked, mugged or simmilar.

From the traffic point of view, street lights make the traffic more secure, not only for vehicles, but allso for all others participants in traffic.

Street lights makes a lot of diference, because it enhances our eye adaptation, ability to focus objects, contrast and contrast sensitivity is better, visual acuity is better, we have better depth perception, and therefore better judgment of distance. 

Based on the above, street lights are very important on roads.