a similar scheme operates in Singapore

I believe, it is called 'Zoning'. A draconian version of HOV; everyone who uses these roads at certain stipulated times, has to pay regardless of vehicular occupancy. I am told that it has dramatically eased traffic snarls and has encouraged car pooling too. But then, Singapore is SO regimented, I don't see how any governemental regulation effected there, can't be a success!