Figure 3.50 A Locality in the State of Colorado

sales or long-term leases, which provide incentives to expand city boundaries and oversupply land, thereby exacerbating sprawl.

Tools and resources for macroplanning include household travel surveys on origins and destinations and transportation models that use survey information for calibration.

Microapproaches are characterized by a narrower geographic and human focus. They also have a shorter time horizon (less than 10 years) than strategic planning and require more detailed preliminary designs. Microdesign is largely analogous to the principles of transitoriented design or transit-oriented development (box 3.14).

Microdesign may be summarized as follows:

Land use distribution (space and time): All functions in large cities cannot be centralized, and the relative locations of developments and transportation links determine travel demand and mode choice. Mixed land uses are important because they infl uence how far one must travel to visit a store or reach work or school. Convenient foot and bicycle access (less than 10 minutes) should be provided from residential housing to shops, services, and recreation, complemented by public transportation facilities for work trips.

Urban densities: Population densities and job locations aff ect transit and land use plans, but are not the only considerations. Lower urban densities tend to boost car use, thereby negatively aff ecting multimodal sectoral plans. However, high densities without adequate planning and services may impede the quality of the lives of residents. Figure 3.50 shows a sprawled residential development typical in developed countries.

Design and orientation of buildings: Large street off sets, parking lots, fences, and greenbelts around buildings became much more common in the second half of the 20th century, owing to concerns about safety, security, noise, and pollution. However, these elements may discourage walking and bicycling because they impose barriers and make trips more circuitous. Thoughtful design is critical.

Road patterns and design: Traffi c volumes on local streets infl uence the quality of life in residential areas. Road designs infl uence driving behavior, traffi c speeds, and safety. Certain road patterns are characterized by low accessibility and connectivity (for example, dead-end streets and cul-de-sacs). Speed limits should be conservative and enforced rigorously in dense residential and commercial areas using signs, police, cameras, and speed humps.

Intersections and crossings: Local access roads wider than 5 meters, equivalent to approximately two lanes, tend to discourage crossing. Intersections with more than one lane in each direction may require traffi c channelization (that is, sidewalks, curbs, pedestrian islands, and markings) and signals. Most congestion on arterials in dense areas is caused by limited throughput at intersections rather than the dimensions of the intermediary road sections. Road width may often be reduced or limited to two or three lanes in each direction and include channelization and modal separation, while minimally aff ecting travel times.

Pedestrian and bicycle environment: Encouraging walking and bicycling by prioritizing nonmotorized over motorized vehicle access (and parking) is a key objective for the urban environment (fi gures 3.51 and 3.52). It is also important to provide pathways or greenways in city blocks,

Figure 3.50 A Locality in the State of Colorado

Source: Digital Globe, Google Earth.