Road density: The space requirement for roads

In the ever-increasing need for transport infrastructure, we often hear about plans for "building more highways," or "widening our roads," floated around as if these are the only solutions to traffic congestion. Well, if  we simply focus on "traffic jams" as our societal problem, these may very well be. In our past write-up, we mentioned about the 16% increase in car sales last year, which generated a lot of excitement to many, as this indicate a booming economy. But that 16% growth means 16% more vehicles in the road, which needs 16% more road space.

That is, we look at it simplistically, and assume that we need the same level of service. So where do we get the 16% more road space? We can build more new roads, expand (widen) existing roads, we can build them on top of each other, stacking them up vertically, i.e. build flyovers or underpasses, expressways, or other similar structures. When one thinks of  a typical town, or small city, there are no problems with any of these, if you have the money. But when we talk of bigger urban areas, these may not be the optimum solutions. On the contrary, they might even worsen the problem.

Most planning initiatives are based on statistics or indicators and it is best to evaluate these thoroughly when faced with a multi-disciplinary dilemma. In land transport, the most common but least noted or used indicator is road density, which measures how much road a certain local government unit (LGU) has. Of course, each LGU is unique, and there is no generalized common standard that is used, but we can always compare figures with averages such as the national average or averages of other countries and cities.

What is road density, how is it computed, and why is it measured? Actually, there are many kinds, depending on how you may use them. In general, there are two ratios — one relating to space, and the other, relating to the population. The first one is purely physical, and is based on the presumption that a bigger area needs more roads. It is the length of roads existing within a certain area and is measured in kilometers per square kilometer (km./sq. km.). The second road density indicator is based on need and use and presumes that each inhabitant needs a certain amount of road space. This is measured in kilometers per 1,000 population (km./'000 pop'n). Both are good baseline metrics and maybe (or should be) used for initial evaluation.

There are other derivative physical (km./sq. km.) indicators. Many will argue that some LGUs have territories which cannot even be used for any development — mountainous areas, steep slopes, deserts, marshland, etc. So instead of the entire area, only the usable area is used in the analyses. Thus we have such indicators as  km./sq. km. of arable area, or buildable area, or habitable area, which excludes areas not fit for human habitation and use.

As we said, we can use this normally with small growing settlements. But in urban areas where land becomes scarce and the competition between uses become acute, there is a need for deeper understanding of the land use and transport use interaction. Land is a finite resource — when we use a part of it for a certain use like roads, we can't use the same for other uses, unless we start building vertically in stacks. In the km./sq. km. indicator, while the main measure is length, those roads have width and thus also covers areas. Whatever area you use for a road, or for its widening, is an area decreased from other land uses. We often forget that land transport infrastructure is also one of  the land uses like residential, commercial, etc.

Increasing road infra from 10% of total space to 20% means that you are decreasing the land available for urban land use from 90% to 80%. If  we  keep on widening our roads, we eventually face the problem of insufficient land use, not to mention the disturbance and dislocation that this brings. There are alternatives to this which have been employed all over the world, mainly premised on increasing space utilization efficiency. One is to build more roads above and below existing ones, and another is to use better and more efficient transport modes. That's why the world's cities are turning to mass transportation.

Cities which were successful were those who understood the problems and worked diligently for the solutions. These will not appear like magic or given to us on a silver  platter. Project development is long tedious process which does not have short cuts. As the world advances into the 21st century, world cities scramble for new and better solutions. Some gets ahead, others will be left behind. A better understanding of the land use/transport continuum will certainly give us an edge.  (to be continued).