What is the purpose for the gaps in the road on the bridges?

Thermal expansion. look it up. heat expands and cold contracts. Even RR track-workers leave a near-microscopic gap to allow for this. There are expansion joints on all bridges over a certain size- One end ( of the span) is fixed- directly on the pier(s) the other end has a certain amount of expansion caused by , mainly temperature variations- hence Thermal expansion.The expansion joints are essentially automatic, and do not require operator attention. I used to work on bridges- and am a long-time railroad buff. If they didn't have gaps then the bridges and highways would crack and break which will cost money for the government to repair (the taxes we pay will pay for the cost of it.

Hope that it helped :)

Mickey this is the answer to 6 copy now