The Neighborhood Speed Bumps
Residents of a neighborhood with a speeding problem petition the city for speed bumps after a child is injured. The city installs bumps on three streets. Within months, traffic on those streets drops, but residents on two parallel streets report heavier traffic and faster driving. Some homeowners near the bumps say they are happy, while delivery drivers complain about delays. A neighborhood association wants to know whether the intervention succeeded and whether to expand it. A council member argues the city should instead lower the speed limit citywide, saying signs are cheaper. The association asks for a sociological reading of what happened and what to do next.
1. Did the speed bumps succeed? Analyze using concepts of intended and unintended consequences.
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The bumps succeeded on their stated target but produced displacement. Traffic on the three streets fell, which is the intended outcome, but volume and speed rose on parallel streets, an unintended consequence that Merton's framework would call a latent function of a manifest intervention. The neighborhood as a whole may not be safer if risk simply moved. The council member's proposal to lower speed limits citywide addresses a broader area but relies on compliance, and signs alone often produce weak effects without enforcement or design changes. The best judgment is that the intervention worked locally but failed at the neighborhood level, so success depends on the unit of analysis. A sociologist would insist on measuring outcomes across the whole area, including streets without bumps, before calling the policy effective or expanding it.
2. What should the association recommend, and what evidence would guide the decision?
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The association should recommend a coordinated approach rather than isolated street-by-street fixes. Options include traffic calming across the grid, closing cut-through routes, or combining physical measures with enforcement and education. Evidence should include before-and-after counts on all streets, speed measurements at matched times, crash and injury data, and resident reports of perceived safety. Delivery delays are a real cost and should be weighed, but they are distributional: drivers bear costs while residents gain safety, which is a classic collective-action tension. The association should also check whether displaced traffic harms lower-income or less vocal streets, since petition-driven policy can favor organized neighborhoods. The reasoning standard is to compare the whole network and to ask who bears the burden. If parallel streets absorb traffic, expansion must be area-wide, not selective.