Cars or buses
- which move more people?
I REFER to Monday's letter by Mr Geoffrey Lim of the Land
Transport Authority (LTA) on the benefits of bus lanes ('LTA takes
care implementing bus lanes').
Mr Lim has pointed out in his numerous replies that a bus carries
80 passengers, while a car has 1.5 passengers. He used the same
point in a reply to a letter last month questioning the benefits of
having a bus lane along Upper Bukit Timah Road ('Special lane
improves bus speeds', Nov 8).
I think we all know a bus carries more people than a car. But that
does not necessarily mean buses can move more people, as Mr Lim
suggested. They can, but it depends on bus frequency.
In his earlier reply, Mr Lim stated that '60 or so' buses an hour
ply the 5km stretch of Upper Bukit Timah Road. This works out to
5,200 bus passengers per hour (assuming 65 buses with a full load
of 80). According to my calculations, a single 5km lane can 'move'
6,389 cars an hour at the speed of 23kmh cited by Mr Lim (using an
average car length of 4.5m and three body length spacing between
the cars, which I believe is generous, given that the cars are
moving at only 23 kmh).
At 1.5 passengers per car, this means 9,583 people per lane - 4,383
more people than by bus, or 84 per cent more. Even if we assume all
65 buses are double-deckers with an estimated full load of 120
people, the single 5km lane can 'move' 23 per cent more people by
car than by bus. How then do bus lanes 'optimise overall usage of
our scare road space', as LTA claims?
Mr Lim mentioned an improvement in bus speeds as one of the
benefits of introducing bus lanes. An increase in bus speeds of 10
to 12 per cent is obviously nice for bus users, but without an
increase in bus frequency, this has no impact at all on the number
of people moved. And what about the impact of the bus lane on
vehicles in the other lanes? Simple logic suggests the flow or
speed of vehicles in the other lanes will suffer. Mr Lim merely
states that this 'remains acceptable'.
In the case of Upper Bukit Timah Road, only '60 or so' buses use
that 5km stretch of lane every hour, but road users in the other
lanes have to contend with an average speed of 23 kmh, and the
possibility of more ERP gantries if the speed becomes unacceptable
according to LTA's definition.
How does this 'balance the needs of different groups of road
users', as LTA suggests?
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