I first learned about the concept back in the 1990’s when I was a graduate student at UP majoring in transportation engineering. The concept on transport gaps was first mentioned in a lecture by a visiting Japanese professor as he was discussing about transport modes, particularly on which was suitable or preferable over certain travel distances and which could carry more passengers. Another time later and while in Japan, I heard about the concept during a presentation of a friend of his technical paper on public transport.
The figure below is one of many possible illustrations of the concept of transport gaps. In the figure, a distinction is made for mass transport and individual transport. As the original figure is likely taken from a textbook or a paper (probably from Japan), shown with a white background are the more conventional modes of transport including subways, urban and suburban railways, walking and a mention of the shinkansen (more popularly known as the bullet train). With a gray background in the original figure is a category on new urban transit systems that include monorails, AGTs and LRTs. If we attempt to qualify local transport modes such as jeepneys, UV Express, tricycles and pedicabs into the graph, the outcome can be like what is illustrated with different color backgrounds in the figure below.
The concept of transport gaps allow us to visualize which modes are suitable for certain conditions where other established modes of transport may not be available or viable. In the original figure, the gap in Japan is filled by new urban transit systems. In our case, gaps are filled by so-called indigenous transport modes such as jeepneys, multicabs, tricycles, pedicabs and even habal-habal (motorcycle taxis).
There are gaps in the Philippine case probably and partly because of the slow development of public transport systems such as the mass transport modes shown in the preceding figure. There was a significant gap right after World War 2 when the tranvia and other railways were destroyed during the war. That gap was filled by the jeepney. There was also a gap in the early 1990’s that was eventually filled by FX taxis. Such gaps can obviously be filled by more efficient modes of transport but intervention by regulating agencies would be required and rationalizing transport services can only be addressed with the provision of mass transport options complemented by facilities for walking and cycling that will complement these modes.