It's not quite as simple as that. At best you get cars parking in the bike lane and it's full of broken glass, at worst you have people cycling into a suddenly

It's not quite as simple as that. At best you get cars parking in the bike lane and it's full of broken glass, at worst you have people cycling into a suddenly opened car door. Separating it properly costs a lot more. The Uxbridge Road (London) is due for some improvements but the high costs of doing it properly have meant they are now only doing shorter sections.