There`s a guided busway in Crawley, about 20 miles north of Brighton. It`s just a few bits of guideway interspersed with lengthy stretches of conventional bus lane (at least, the bits I saw were). It was built in 2002, late, over budget and had to be closed for long periods due to emergency repairs. It also means that only buses with the special guide wheels can use it, so you end up with a situation where the majority of bus traffic is in the normal traffic lanes and getting caught in the same congestion as everything else. My brother mentioned it as a massive waste of money, and he worked for Crawley Council at the time! I do agree, perhaps a two way bus lane would be the best option. You could then put tram rails in as and when required with the buses under contra-flows and temporary lights, and that would still cause less congestion than fitting tram rails to a normal road.
IMHO the Cambridge scheme was a massive white elephant. The heavy rail option may not be the best, and what would happen if no-one used the guided buses? After all, it`s not exactly a hobby of mine, riding round all day (I have to as I`m a bus driver...it`d be too much like going to work on my day off) so really why would I want to? You`d be left with a closed busway that has just cost millions of pounds to build that could have been a railway that could take peopel from one end to the other in minutes.
Isn`t there also a plan to build 2 more platforms at Cambridge station?