Road Congestion: Physical Limits vs Information-based Orchestration

On 1 July, the Straits Times published a report titled "ERP system: From gantries to satellites" describing LTA's intent to invite technology firms to test such a system next year.

The article notes that the new system "will allow LTA to extend its ERP coverage to congested roads anywhere on the island, without having to install more gantries, which cost about $1.5 million each" and that "the system can be adjusted so that motorists pay only if they are approaching a section of congested road. The in-vehicle unit can also be used to notify them that they are about to enter a stretch of road that attracts a charge".

However, a rudimentary analysis of our transportation system would lead one to conclude that given its current characteristics (that is to say: road network, vehicles on the road, etc), road congestion is highly insensitive to information-based methods of congestion reduction such as ERP.

There are physical limitations to the level of throughput a given infrastructure can provide. Even if we were capable of optimally orchestrating traffic (centrally routing all vehicles to ensure optimal performance for the transportation system), a network of heavily jammed roads would be better ameliorated by, for instance, widening a few major roads or reducing the number of vehicles on the road.

In fact, a study of the major means of transportation (bus, train, private vehicle) would clearly show that the current transport infrastructure is operating at or close to its limits. The promotion of information-based systems in tune with building an "information economy", but we should not lose track of reality, bearing in mind that it is the physical system providing the service. When a system is operating near its limits, its capacity should be increased or its load decreased. Only where an information system can be shown to provide a clear improvement in throughput should any investment be made. Currently, both satallite and land-based ERP fail this test.

Contrary to the claims of the July 1 report, it is not the gantries that have hit their limits, it is the road network.