Person-trips and the term “modal split”

Published in The Freeman (Philippine Star), March 1, 2012

Last a Last week, we talked about the “person-trip,” the basic unit of transport that is used to plan for a transport system of a given city.  A person-trip is a trip by one person in any single mode of transportation.” Adding up all the person-trips generated within a city will give you the transport demand, which has to be serviced by vehicles and the road system. Its almost impossible to have a balanced supply of roads and vehicles. We complain of insufficient roads and of the shortage of vehicles. Usually it’s both. But what people always whine the most is “traffic,” or more correctly, traffic congestion. Traffic problems is not the lack of roads or vehicles to carry the population – it is simply the insufficiency of roads space to carry the vehicles! This difference is crucial!

For a small town or barrio, this issue is simple. But as it grows into a city or ultimately a metropolitan area, the problem complicates into highly mathematical and scientific calculations of supply and demand. The basics remain the same – person-trips are generated because people generally travels daily from home to work, go to school or church, attend to personal and family matters, or do social and recreational activities. But the sheer number of different trips plus the complexity of land uses as discussed in previous writeups makes it difficult to solve without using transport science. From person-trip, we evolve to the term “modal split.” No, it’s not an ice cream dessert!

We said person-trips maybe classified as to the purpose: home-to-work, school or church, personal/family matters, or social/recreational, or as to mode: walking, habal-habal, trisikad, tricycle, multicab/FX/megataxi, jeepney, V-hires/GTs, minibus, bus, LRT/MRT, taxis and private cars. Let’s show a typical example. On a particular day in 2010, going into Cebu City along N. Bacalso Ave. or Gov. Cuenco Ave., during the peak hour of 7 – 8 AM, the vehicle flow is composed of the following: cars-32%, taxis-8%, trucks-3%, jeepneys-26%, bicycles-8%, and motorcycles-23%. Traveller flows on the same peak period and direction shows a different pattern: by car-9%, by taxi-2%, by PUJ-74%, and by two-wheel vehicle-15%. The vehicle shows reflects the vehicular traffic characteristic on the road, the passenger flow reflects the total person-trips mode share, or “modal split.”

This is lifted from the studies done for the proposed Bus Rapid Transit (BRT). But whether for BRT or any other kind of transport system, it is imperative that the existing transport conditions be studied thoroughly, especially on what the people presently use. In the above example, we can deduce that private car journeys carry just 12% of trips despite accounting for about 30% of the vehicles on the road, while jeepneys carry 65% of the trips while making up just about 25% of the vehicles on the road. That’s on the average; the actual figures for N. Bacalso and Gov. Cuenco are different from each other, which actually shows which part of the city is more affluent, … in general. I won’t tell you which, but you probably know already.

In general, while there maybe as many modes as there are classifications of vehicles as registered with LTO, it ultimately boils down to the share of person-trips using private cars, and those by public transportation. The latter evolves to “public mass transportation” in bigger cities such as Metro Manila or Metro Cebu. The modal split in Manila is different from Metro Cebu. The modal split actually describes what kind of city it is and how its population moves daily. Planning simply attempts to shape or “shift” the “modal share” for a better more livable city in the future. (to be continued)

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