But before we ask that, we have to understand what a Traffic Impact Assessment (TIA) is and what is it supposed to show? It’s self-explanatory especially if we compare it with another more familiar document – the Environmental Impact Assessment (EIA), which is a study of what the environmental impacts will be if we do a certain project. Under DENR Administrative Order (DAO) No. 96-37, projects are supposed to prepare such the EIA before an Environmental Compliance Certificate (ECC) is issued. A TIA is supposed to be similar, though not yet required by law.
Simplifying a little bit – a road, just like anything else that carries or contain other things, has a certain limit of capacity. Usually, the unit of measure is vehicles per hour (or per day). When traffic volume approaches the capacity, or exceeds it, then we have what we call congestion, more commonly known as “traffic jams.” Of course, the goal of traffic management is to do everything so that the capacity is not exceeded. That is also the goal of transport planning (which is not synonymous with traffic management!). In the analogy of a glass being filled with water, we see to it that the glass does not overflow.
Take a look at an existing street with an existing traffic flow. Let’s assume further that the traffic volume is half (or 50%) of its capacity. Then we say that the VCR (volume-capacity ratio) is 0.50. Now, suppose a 50-story residential condominium is built along that street with, say, 1,000 units. Further, let’s suppose that 20% of the future owners of the condo units will own cars. Then, we know that after the condo units are built and sold, there will be 200 more cars which will use that street especially in the morning when people go to work and in the evening when people go home. So the volume of vehicles using the street will increase but the capacity will remain the same, thus, the VCR will increase. Let’s assume 0.55.
Suppose another condo is built with exactly the same size. For simplicity, we can predict the VCR will increase to 0.60. A third condominium built along the same road will increase the VCR to 0.65. If we continue, warning bells will start ringing in the transport planners mind when the VCR’s exceeds 0.85 – this is actually approaching congested conditions. This will slow down traffic and increase travel time. Eventually, for VCRs of 1.0 and above (it’s possible), gridlock or bumper-to-bumper traffic occurs. And the government is tempted to say no to the 7th or 8th condo projects.
The problem here really is one of fairness. When do we allow and when do we deny. The 7th and 8th applicants will be denied simply because they applied later. If they applied first, they would have been allowed. It all boils down back to the land use and transport planning issue. Land use should have assumed already future traffic contributions. Transport planners should have considered already the trips generated at full land utilization. Provisions for more efficient transport modes and technology should already be in place.
This is why the TIA is important. But a TIA system has to be legislated, same as the EIA system for the environment. Traffic impact assessment is primarily the job of government. Projects will prepare theirs but within the overall TIA framework of the government. Let’s wish our local governments will be up to the task. One actually already did – Laguna. For more detailed readings on what we are talking about, I recommend Resolution No. 28 and Provincial Ordinance No. 2, both series 2000, of the Provincial Government of Laguna. The HLURB has also issued theirs, for large-scale development. What we need is a holistic yet flexible plan, not reactions to issues, especially in a fast-changing urban landscape like Cebu.