Dec 12, 2008
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?
Jatin Doktor
Source
http://www.straitstimes.com/print/ST+Forum/Story/STIStory_313315.html