There are few street lights on some highways because of safety, high requirements, and costs.
- Safety: There are seldom any non-motor vehicles or pedestrians on the highways. Besides, the roads on the highways are always flat and smooth. So the highways are relatively safe.
- High requirement: If applying the common street lights in the cities, the lighting is usually uneven and discontinuous. With this light, the drivers are likely to experience eye strain. But improving the lights will cost a lot of money.
- Costs: The highways are very long roads. To meet the lighting requirements, they need a large number of street lights. Running costs, maintenance costs, and other costs are too expensive.
More reading: Standards about Street Lighting