The theory of the Community Builders and academics of the 1930’s played out far differently than intended. Rather than building villages and communities of people, the transportation infrastructure created the basis for support of the retail typologies we see in suburbs today.

Roads affect retail formats in two important ways: street configuration and market access.

The immediate street configuration, including right of way, lanes and width, setbacks and traffic speed are one category. Within this category, there is a relationship between the speed of traffic and the nature of development on the street. While the causation is a bit like the chicken and the egg, the relationship is quite clear. Fast traffic begets buildings with large setbacks and large separations. Locating buildings close together and close to the street tends to calm traffic. In fact, building to building distance and street width is more significant than street width alone in reducing traffic speed. Highways with faster traffic speeds require a longer reaction time for the driver to identify the turn and slow down and thus suburban businesses prefer larger setbacks for parking and visibility as well as identifiable signage. Suburban highways usually have minimum setbacks to preserve this model and the speed of traffic. Curiously, higher traffic speed does not guarantee greater throughput, which is most efficient at 30 miles per hour- a speed that happens to coincide with human scale or main-street retail built close to the street accommodating pedestrian traffic as well.

Roads networks also determine the access a retail business has to its market. In suburban highway conditions this is measured in vehicle counts, which is really a proxy for understanding the number of people or households in the trade area for whom location has easy access and visibility. In the suburbs where travel speeds are higher, supporting low density housing, the effective area served by a retail store is greater, and as we have seen with the ideas of retail gravitation, stores are increasingly encouraged to be as large as possible to capture as much of the local and regional market as it can. It is common to justify the success of the resulting big boxes and discount retailers by their sales, despite public opposition to their business model or architecture. However, these “actions of the general public”, supporting the stores with their wallets, should not be read as a universal economic superiority or necessity of the format, but evidence of its appropriateness to the surrounding suburban conditions. Where smaller scale road networks provide local access with slower speeds to more populated areas and many people walk or use public transportation, access to such a wide geography is not necessary and smaller formats are still efficient. This is because of the other implication of retail gravitation: that proximity to markets is a balance against shear size. Consequently, different retail formats are best suited to different road networks and population distributions.

-gk