Understanding

Rapid Transit Capacities part 4 - Needed capacities

The usual problem with the discussion on specific rapid transit capacities is to look at theoretical figures and not on problem-specific/location-specific ones. One immediately concludes that rail has a higher capacity than bus-based transit, which is true when we are talking of metros --high-speed, high-capacity, underground trains in megacities (London, Paris, Tokyo, etc.). As we said last week, rail capacities vary very widely depending on the kind/type. So do BRTs.

When you’re talking of demands beyond 40,000 passengers per hour per direction (pphpd), you have no option but go underground by rail. But less than that, you have a choice among various rail types as well as various bus-based modes, and the decision becomes more of economic efficiency --which would generate the highest economic benefit for the cost incurred. In most cases, BRTs give higher values.

But comparisons are often misleading when specific demands are not analyzed. For example, in a medium-sized city, the present demand might be 10,000 pphpd and the expected demand in 25 years might be 15,000 pphpd. We can’t conclude that rail is better because it can have a capacity of 50,000 pphpd. We won’t reach that anyway, and it is also counterproductive to build capacities in advance to last for 100 years! The saying, “build them and they will come” does not necessarily hold true – demand progresses based on other factors less associated with simply building the supply.

Thus, transport infrastructure planning relies heavily on getting an accurate forecasting procedure for future ridership demand over a 20 to 30-year planning period. It’s usually advisable to already conceptualize expansions and/or new infrastructure after that, but the technical, financial, and economic analyses are usually dealt with within a 20 to 30-year operating period. And for transport of medium-sized cities, this usually hovers around Light Rail Transit, monorail, and BRTs.

At these ranges, it is important to realize the comparative capacities of systems. And most capacities depend on their operating environments. For example, the capacity of MRT-3 in Metro Manila (at present) is around 14,000-18,000 pphpd. Bogota (Colombia) BRT carries 40,000 pphpd, and Guangzhou (China) BRT reaches 35,000 pphpd. MRT-3’s design was 23,000 pphpd but it can be expanded to a high of 48,000 pphpd. Within a range of 10,000-40,000 pphpd, both rail and bus-based systems work just fine and the only question as to choice, really, is how much they cost to build and how much they cost to operate. Since BRTs cost around 20 percent of that of LRTs, economic managers generally prefer them over rail. Especially in developing countries where huge capital investments put intense pressure over social development.

At the end of the day, the question boils down to what solution is the better option to address society’s needs, to provide mobility to the majority, especially for those who can’t afford cars, as well as serve the disadvantaged sectors such as the women, the elderly, children, and people with disabilities. These are the crucial considerations. (To be continued)