Also, nobody talks about the cost of raising and lowering a drawbridge.
Worked at a civil engineering company that worked on a major drawbridge project. Minimising the number of times it needed to be opened/closed was a major concern and huge point of contention.
I assumed it was due to the height of the ships that typically passed. Probably costs more to build the bridge higher so you don't have to raise it as often, so they fight about lowering costs and minimize the number of times they raise the bridge.
Traffic mainly, but also maintenance. Mechanisms needed to be inspected/serviced every N openings. Although the big fight was basically that 'Team Road' wanted the bridge to open twice a day at fixed times and if a boat missed its slot it just had to wait, while 'Team River' wanted the bridge to open within 10 minutes of any boat showing up.
Worked at a civil engineering company that worked on a major drawbridge project. Minimising the number of times it needed to be opened/closed was a major concern and huge point of contention.