@M A Walters: Hills Road Bridge
No, I haven't seen this bridge - I don't live or work in Cambridge though I know people there who cycle extensively and are disgusted by the local paper's attitude to cyclists, motivated entirely by the advertising revenue it gets from car dealers. I think they mentioned this bridge the last time I saw them but are away at the moment so I can't get details from cyclists' point of view. Looking it up on the web seems to indicate that the disruption is temporarily worse due to road works, and is mostly due to the guided bus which I wouldn't defend in the name of public transport.
Measures that encourage cycling ought to be applauded by car drivers - congestion caused per traveller is on average far greater when those travellers are being transported by car than by bicycle. You've noticed the increase in cyclists during term time - would you prefer that each of them were driving a car instead?
I presume you don't venture out on the roads on a bicycle much, if at all. If you did, you'd know that, irritating though bad cyclists are, because they are not wrapped in a tonne of metal with dozens of horsepower pushing it along, they are an order of magnitude less dangerous than bad motorists, and tend to be suicidal rather than homicidal. Sitting in traffic jams you will be irritated by all the cycles whizzing past, and because you will see more of them then the cars represented by the bumper of the stationary vehicle in front of you, you will be exposed to a disproportionate number of bad ones. Dozy motorists not looking out for bicycles (however well-lit and well-behaved their riders), or aggressive motorists, are the cause of most of the serious collisions; the blame for very few organ donations rests entirely with the cyclist.
Cambridge is flat. If you have a commute of less than five miles or so and are able-bodied, there really isn't any reason why you shouldn't cycle most of the time. Of course there is a risk, but it is low if you are prepared, sensible (get some training), and if you don't spend half your time and salary at the gym anyway, your life expectancy will go up by about 10 years. I commute 10 miles each way, with quite a lot of climb, but that's getting fairly hard-core and I wouldn't expect those other than the dedicated to follow suit.