Dec 19, 2008
ON THE ROAD
I REFER to Mr Jatin Doktor's letter last Friday, 'Cars or buses - which move more people?'
Mr Doktor estimated the capacity of a road lane at 6,389 cars per hour along Upper Bukit Timah Road, which would move up to 9,583 people per hour per lane. This was then compared with the bus lane carrying some 5,200 bus passengers per hour.
In fact, based on Mr Doktor's assumptions of car spacing (average car length of 4.5m and three body length spacing between cars) and a travel speed of 23kmh, there would be a total of 1,278 cars passing a specific point every hour along one lane of road. This is the throughput capacity of the road lane.
Unfortunately, Mr Doktor appears to have made an error by multiplying by five, arriving at 6,389 cars per hour, on account of the 5km length of Upper Bukit Timah Road.
The length of the road lane has no effect on the throughput capacity, in the same way that the length of a water pipe does not increase the flow rate of water through the pipe.
Our monitoring of traffic along Upper Bukit Timah Road during the morning peak hours shows that the throughput is about 1,500 vehicles per lane per hour. If we take the average number of people carried by a car to be 1.5 and that carried by a single- deck bus to be 80, it would work out to about 5,000 passengers per hour on the bus lane, compared with 2,250 passengers by car on a normal road lane.
Hence, bus lanes better utilise our limited road space and favour more people.
The bus lane scheme is one of a series of initiatives to improve bus commuters' overall journey experience. Bottlenecks at congested stretches of roads would delay the travel of not only on-board passengers, but also commuters further downstream in terms of unreliable waiting time.
With more bus priority measures, buses can keep to their schedules better, and bus commuters can enjoy faster and smoother journeys. Given our land constraints, we need to strike a balance in meeting the needs of different groups of road users.
We seek public understanding and support for our efforts in improving the travel experience of all road users and we thank Mr Doktor for the opportunity to clarify.
Geoffrey Lim
Deputy Director Media Relations
Land Transport Authority
[If you like math, you'll love to try to understand this reply. This is a good reply. But not all will understand.]
ON THE ROAD
I REFER to Mr Jatin Doktor's letter last Friday, 'Cars or buses - which move more people?'
Mr Doktor estimated the capacity of a road lane at 6,389 cars per hour along Upper Bukit Timah Road, which would move up to 9,583 people per hour per lane. This was then compared with the bus lane carrying some 5,200 bus passengers per hour.
In fact, based on Mr Doktor's assumptions of car spacing (average car length of 4.5m and three body length spacing between cars) and a travel speed of 23kmh, there would be a total of 1,278 cars passing a specific point every hour along one lane of road. This is the throughput capacity of the road lane.
Unfortunately, Mr Doktor appears to have made an error by multiplying by five, arriving at 6,389 cars per hour, on account of the 5km length of Upper Bukit Timah Road.
The length of the road lane has no effect on the throughput capacity, in the same way that the length of a water pipe does not increase the flow rate of water through the pipe.
Our monitoring of traffic along Upper Bukit Timah Road during the morning peak hours shows that the throughput is about 1,500 vehicles per lane per hour. If we take the average number of people carried by a car to be 1.5 and that carried by a single- deck bus to be 80, it would work out to about 5,000 passengers per hour on the bus lane, compared with 2,250 passengers by car on a normal road lane.
Hence, bus lanes better utilise our limited road space and favour more people.
The bus lane scheme is one of a series of initiatives to improve bus commuters' overall journey experience. Bottlenecks at congested stretches of roads would delay the travel of not only on-board passengers, but also commuters further downstream in terms of unreliable waiting time.
With more bus priority measures, buses can keep to their schedules better, and bus commuters can enjoy faster and smoother journeys. Given our land constraints, we need to strike a balance in meeting the needs of different groups of road users.
We seek public understanding and support for our efforts in improving the travel experience of all road users and we thank Mr Doktor for the opportunity to clarify.
Geoffrey Lim
Deputy Director Media Relations
Land Transport Authority
[If you like math, you'll love to try to understand this reply. This is a good reply. But not all will understand.]
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