Noise benefit isn’t marginal. Central London average speed is 7 to 10 mph (11 to 16 km/h) so engine noise is significant. There is lots of idling traffic: traff

Noise benefit isn’t marginal. Central London average speed is 7 to 10 mph (11 to 16 km/h) so engine noise is significant. There is lots of idling traffic: traffic lights, taxis at cab ranks, buses at bus stops, everyone in a jam - removal of idle noise is particularly significant.