http://news.bbc.co.uk/1/hi/uk_politics/3628631.stm

I don't think physical "traffic calming" is good for drivers or
cyclists. Speed cushions are particularly horrible as they encourage
drivers not to give you any clearance when overtaking, for fear of
hitting the blasted things head-on.

As a driver I would much rather see measures that don't knacker your
suspension if you are driving within the limit. Some speed cushions in
30mph zones can only be negotiated at 20mph (unless you drive a large
4x4 or a company car, haha) and chicanes just increase congestion and
pollution.