Conventional logic tells us more homes equal more residents equal more cars equal traffic jams, especially during rush hour. Traffic concerns are regularly cited at public hearings where housing proposals are considered.
At the level of individual developments, new auto-trip generation is usually so marginal in comparison to all existing traffic, from all sources, as to be insubstantial in contributing to traffic congestion. Traffic studies conducted on individual developments conclude this, again and again. Moreover, rush-hour auto-travelers are under-represented among residents of multi-family housing generally. And importantly, housing development significantly enables new household formation, more than it generates new population growth. Finally, municipalities can use zoning regulations to mitigate traffic and promote pedestrian-friendly design.
At the macro level, building enough housing, across Massachusetts, to enable both population growth and economic growth will contribute to already serious traffic, unless other changes are made. Economic growth gives more residents the resources to drive cars; population growth brings new drivers. The solution is not to be found in housing shortage and escalating levels of poverty that keep people carless. The solution must be in comprehensive planning and investment in modern multi-modal transportation systems, as well as implementation of traffic management policies and programs. The solution is also to locate more housing in areas that are walkable and well served by (current and potential) public transportation and bike infrastructure.
A common concern about new development relates to the availability of on-street parking. Nobody enjoys circling to find parking. New residents could bring competition for on-street spaces. The conventional response to these concerns is to require new developments to contain ample on-site parking to serve any potential demand for parking by residents and visitors. This policy response causes many additional problems. Parking gets overbuilt, more provided than needed, at significant cost, in terms of construction materials, design, and environmental impact. Ample on-site parking encourages driving and attracts drivers. The parking requirements end up contributing to traffic. There are many tools for managing availability of on-street and public parking that should be used instead of requiring on-site parking for new development.
Municipal minimum parking requirements have been shown to increase rents and contribute to making homes unaffordable. Change is happening though as many communities reexamine and reduce (or remove!) their minimum parking requirements for residential development.
Analysis of parking requirements has shown that the number of parking spaces built is often equal to the number required by a municipal minimum parking requirements. Thus, these policies determine the level of parking provided and that level is higher than what would be supplied in their absence. Each parking space constructed adds to overall development costs and in the case market rate housing this cost is passed on to future homeowners and tenants thus decreasing affordability. In affordable housing developments these requirements increase the amount of subsidy required. A recent study in Seattle, where parking requirements were reduced or eliminated found that reducing parking requirements led to less parking being provided, but it varied depending on development type. Overall developers in Seattle built 40% less parking than would have been required before the reforms saving an estimated $537 million. 20
Massachusetts needs both more homes and better transportation solutions. There are many policy tools available to manage parking and traffic that government can implement, beyond restricting housing or mandating too much onsite parking. At the local level transportation demand management programs can require developers to incorporate appropriate programming into large developments. For example, the City of Boston requires all large new projects to reduce vehicle trips. Options to do so include subsidizing public transit for tenants, market-based pricing of parking (i.e. unbundling parking from rent), encouraging biking through bike and e-bike sharing and providing additional parking for bikes, encouraging carpooling, and improvements to bus stops.