Understanding how the game spawns elements can help you pre-plan:
Traffic lights were rebalanced. In Build 16932973, a traffic light actually increases throughput at a 4-way intersection by 23% (tested by community data miners). However, placing two traffic lights within 8 tiles of each other causes a "cascade failure." Rule of thumb: One traffic light per neighborhood, max. Mini Motorways Build 16932973
The most common mistake is connecting a row of houses directly to a row of buildings across the street. Understanding how the game spawns elements can help