Figure 3.47 The Input-Output Framework of Transportation Interventions

Independent inputs (mostly given or not controlled): • Geographic constraints • Demographic and economic conditions • Climatic and atmospheric conditions • Social norms and historical practices

Dependent inputs (controlled to some degree): 1. Policy, legislation, and regulations 2. Institutions 3. Physical systems, technology, and spatial planning 4. Stakeholders 5. Economic and financial aspects

Transport interventions:

A. Land uses and travel demand

B. Infrastructure and services

C. Vehicle fleet and fuel supply

Desired outputs

(objectives to be maximized): • Mobility • Accessibility • Quality • Efficiency • Safety • Affordability

Undesired outputs (to be minimized): • Implementation time and life-cycle costs • Accidents and incidents • Global and local emissions • Impact on land, water, and energy consumption

Figure 3.47 The Input-Output Framework of Transportation Interventions

Source: Author compilation (Georges Darido).

The desired outputs noted in table 3.17 may be used to defi ne project development objectives and program indicators for monitoring and evaluation.1 Reducing undesired outputs or outcomes is important in the eff ort to ensure sustainable transportation interventions. For example, international experience suggests that signifi cant shares of private vehicles and low urban densities boost fuel consumption (that is, energy per capita), which increases travel expenditures, infrastructure investment, and the emissions of local pollutants (mono-nitrogen oxides, sulfur oxides, carbon monoxide, and particulate matter) and global pollutants (carbon dioxide [CO2] and other greenhouse gases). Table 3.18 provides sample transportation sector outcomes in several cities around the world. The spatial, physical, and technological factors contributing to these outcomes are described in subsequent sections.

Sustainable transport interventions should be linked to a continuous and comprehensive planning process that involves incremental implementation or a building block approach. The selection and sequencing of interventions should depend on enabling conditions and the implementation of complementary measures. In other words, maximizing mobility and accessibility may be achieved only if reasonable levels of safety, economic viability, and fi nancial sustainability have been ensured. The World Bank Transport Strategy emphasizes that clean, safe, and aff ordable infrastructure and services represent the main aims of urban transportation users. This chapter describes sustainable transport interventions under each of the fi ve controllable inputs listed (see fi gure 3.47), distinguishing between enabling conditions (stage I) and additional measures (stage II) that are substitutes or complementary actions.