Buses have a much lower modal shift ( ie attracting car drivers) capability than trams

Comparative Mode-Shift to Quality Bus Schemes

4.33 While the effectiveness of light rail in attracting car users has been clearly demonstrated, the ability of bus-based schemes to affect significant mode shift in the UK remains largely unproven. A comprehensive study of existing schemes found overall potential passenger uplift from bus quality initiatives27 ranged from between 4.1% and 6.4% in the medium term (i.e. 3-5 years after implementation of all measures).

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4.37 These responses are encouraging but, in comparison to light rail, suggest a much lower level of car transfer: • Typically, around 20% of peak light rail users have been found to transfer from car. In a peak hour, a typical system operating at, say, 6tph would have resulted in c.240 cars per hour removed from the road network. • Similarly, 20% of new bus users in a quality corridor might transfer from car and a 20% uplift in total demand might be achieved. At an overall level of service of, say, 30bph then c.40 cars per hour would have been removed from the road network.