The car as a lock-in

The car has gained a dominant position in present-day mobility and transport, not in the least because the costs of pollution, noise, accidents, congestion and use of space are not or only partly internalised. It makes other modes of transport less attractive, not only economically but also regarding other quality of life aspects (health, safety, esthetics). In the long run, it did and does cause people to move to suburbs, which further increases the need for vehicles and erodes the tax base for mass transit systems and makes urban centers less attractive. In the low-density suburbs, neither walking and bicycling nor public mass transit transportation systems are attractive options and the car mode becomes a lock-in. It has unfolded in the United States as well as in several low-income countries to its extreme. The underlying dynamics can be explored with a system approach, which focusses on two subsystems: the interaction between car ownership, travel time and road construction, and the interference between the car and public transport (Sterman 2000). Other modes of transport, such as bicycles, motorcycles and airplanes, are  not included.

Four loops in the transport system

There are three stocks in the CLD of the transport system considered: roads, the car fleet and the public transport fleet in the CLD, each of them being a cause of inertia (Figure 1). There are four loops. The first one is the road-congestion loop. It portrays the incentive to construct new road capacity in response to increasing travel time due to congestion and the subsequent public pressure to do something about it. Given a desired travel time, the system would experience an increase in road capacity over time. Because there is a long delay in road construction and because desired travel time may change due to external factors (think of audio/video, mobile phones and GPS-navigation, which influence the perception of time spent in the car and the options to control it), one can expect the system to show overshoot and undershoot behaviour.

Figure 1 A causal loop diagram (CLD) of parts of the transport system. The four loops are indicated in bold (based on Sterman 2000).

Congestion decreases the attractiveness of car travel, for most people. When new roads are built, transport capacity goes up and car travel time will go down. Given some desired travel time, there will be less (pressure to reduce) congestion and the number and length of car trips will probably go up too (car use loop) . This will increase travel volume. It will also induce people to buy more cars, which, in combination with increasing population and economic activity in the region, is another drive towards larger traffic volume (car ownership loop). As a consequence, people will after some time again experience congestion and longer travel times – and start to push for more roads.

There is a fourth loop: the public transport loop. If no new roads are built, congestion goes up and the actual travel time by car start to exceed the desired travel time. For some people at least, the attractiveness of car driving goes down and they start looking around for alternatives. One such alternative is bus, tram, metro or train . It increases the use of public transport, which, at least in the short term, leads to lower service levels due to overcrowding, seat capacity problems and the like. This exerts a downward pressure on use but it also tends to increase utilisation rate and, therefore, decrease the cost and, hopefully, the price of a trip. In the longer term, the response is to invest in additional public transport capacity. If this translates into better coverage and service levels, the public transport attractiveness increases relative to car driving.

Pathways to more public transport

Clearly, quite different pathways are possible, as the large differences in transport infrastructure between European cities and American cities show. A lock-in for public transport at a low level is sketched by Sterman (2000) and labelled the Mass Transit Death Spiral. Because public transport systems have rather high fixed costs (infrastructure, personnel), the operating company is faced with a budget deficit once the number of passengers drops. If ticket prices increase and service and frequency levels reduce in response, the number of passengers drops even further and a downward spiral sets in. Constructing more roads reinforces the negative spiral. The mechanism is particularly hard to overcome if the public transport service degrades because of car congestion. In many urban areas in the world, people are accepting ever longer car and bus travel times .

A very different process can unfold, too. The public transport authority plans for and construct new infrastructure. It takes time, as with road construction. It needs public hearings and construction permits. The construction of buslanes in the city of Utrecht took more than ten years from inception to construction. It also requires upfront investments for which loans and, therefore, the prospect of steady revenues are needed. At this point, failure often sets in due to political and institutional obstacles – for instance, lack of financing due to creditor’s desire for high and fast profits. But if the local authorities and the public or private operator succeed in overcoming these obstacles – for example, by attracting more people – a positive loop starts. The utilisation rate goes up, revenues go up and there is room for new infrastructure such as bus lanes and greater schedule/route coverage, and other ways to attract passengers such as increased reliability, cheaper tickets, electronic payment, additional comfort and so on. Such a positive loop can be reinforced by popular concern about local air pollution and inner city destruction and by high parking fees as the price of limited space goes up.

These dynamic processes create a lock-in effect for public transport at a high level. It can be observed in many European cities where electronic ticketing, road use privileges and other technological and economic measures are increasing accessibility and comfort at affordable prices. This conceptual scheme, simple as it may be, highlights some of the behavioural responses in the transport system that are overlooked in purely technical analyses. It explains why such systems often show oscillatory behaviour over time and why well-intended policy measures are sometimes ineffective or even counterproductive. It also reveals some of the intricacies of operating a ‘public goods’ system, an issue of great concern in sustainability science.

Literature

Sterman, J. Business Dynamics – Systems Thinking and Modeling for a Complex World. Boston: McGraw Hill, 2000.