Mass transit, above or below the ground?
Wednesday, 17 March 2010
Shafiqul Alam
Whether the mass transit system of Dhaka city would be above or under the ground is a matter of political decision. For obvious functional reasons, there is no alternative to an underground mass transit system for the city's old as well as new areas. Elevated alignments offer substantially lower initial construction costs.
But above the ground system would requires rehabilitation costs.
Elevated alignments involve long-term environmental impact. Outside the city center, elevated alignments offer longer and less expensive transit system.
Underground railway, capable of transporting 50,000 to 60,000 passengers per hour per direction suits needs of growing cities more. Radial corridors link it to city centres. Decisions makers nowadays worry about environmental sensitivities unlike in the past.
The underground system does not provide visual obstruction on the city surface. Moreover, a new elevated alignment more often does not suit or cannot be accountable on space starved city surface. The underground railway can serve traffic requirement better with less travel-time facilitating uninterrupted journeys.
A mix of cut-and-cover tunneled construction made underground railway an easier task. The relative construction cost and impact on traffic and businesses during construction often influence or determine the decision. Some cities opted the cut-and-cover tunneled option despite the cost. At least Amsterdam found both the options similar from the cost point though the cost of stations were higher for the tunnel option. But for Singapore the tunnel cost less than the cut-and-cover option. Lille opted for the cut-and-cover alignment as a better urban solution. Budapest opted for cut-and cover option to replace aging utilities. Several other cities opted for the tunnel solutions to preserve trees, historical places and minimise surface disruption on side walks. The City of Tokyo opted for the tunnel due to public opposition to the cut-and-cover approach.
For saving time at least 16 cities opted for the under ground railway. Underground railway travels faster. Bus or tram also saves commute time in Budapest. In Taipei, the Tamshui line saves considerable time per trip. Fully grade-separated surface and elevated solutions also saves travel time .But it may not be an option due to inadequacy of surface space.
At least in 11 cities mass transit meant fewer cars. A new underground in Sendai reduced the number of cars and buses in the city centre. In Rennes, it reduced private vehicle mileage by 5.8 million km per year. In Toulouse, private car traffic dropped by 5.0 per cent. In Mexico City, traffic speed increased by 20 -30 per cent a metro line.
At least 12 cities reported indirect advantages of the underground system. The underground railway became starting point of urban development in several cities including Mexico City. The system saved space taken by vehicular traffic. In the City of Toulouse, it created space for sidewalks.
The writer can be reached at: shafiq@iidfc.com
Whether the mass transit system of Dhaka city would be above or under the ground is a matter of political decision. For obvious functional reasons, there is no alternative to an underground mass transit system for the city's old as well as new areas. Elevated alignments offer substantially lower initial construction costs.
But above the ground system would requires rehabilitation costs.
Elevated alignments involve long-term environmental impact. Outside the city center, elevated alignments offer longer and less expensive transit system.
Underground railway, capable of transporting 50,000 to 60,000 passengers per hour per direction suits needs of growing cities more. Radial corridors link it to city centres. Decisions makers nowadays worry about environmental sensitivities unlike in the past.
The underground system does not provide visual obstruction on the city surface. Moreover, a new elevated alignment more often does not suit or cannot be accountable on space starved city surface. The underground railway can serve traffic requirement better with less travel-time facilitating uninterrupted journeys.
A mix of cut-and-cover tunneled construction made underground railway an easier task. The relative construction cost and impact on traffic and businesses during construction often influence or determine the decision. Some cities opted the cut-and-cover tunneled option despite the cost. At least Amsterdam found both the options similar from the cost point though the cost of stations were higher for the tunnel option. But for Singapore the tunnel cost less than the cut-and-cover option. Lille opted for the cut-and-cover alignment as a better urban solution. Budapest opted for cut-and cover option to replace aging utilities. Several other cities opted for the tunnel solutions to preserve trees, historical places and minimise surface disruption on side walks. The City of Tokyo opted for the tunnel due to public opposition to the cut-and-cover approach.
For saving time at least 16 cities opted for the under ground railway. Underground railway travels faster. Bus or tram also saves commute time in Budapest. In Taipei, the Tamshui line saves considerable time per trip. Fully grade-separated surface and elevated solutions also saves travel time .But it may not be an option due to inadequacy of surface space.
At least in 11 cities mass transit meant fewer cars. A new underground in Sendai reduced the number of cars and buses in the city centre. In Rennes, it reduced private vehicle mileage by 5.8 million km per year. In Toulouse, private car traffic dropped by 5.0 per cent. In Mexico City, traffic speed increased by 20 -30 per cent a metro line.
At least 12 cities reported indirect advantages of the underground system. The underground railway became starting point of urban development in several cities including Mexico City. The system saved space taken by vehicular traffic. In the City of Toulouse, it created space for sidewalks.
The writer can be reached at: shafiq@iidfc.com