Understanding Boston's geography
Why Boston's drive times defy radius math.
Boston's road geometry — narrow, non-grid, and frequently one-way — produces drive-time polygons that look nothing like the clean circles a planner might expect. The Charles River constrains crossings between Boston, Cambridge, and Somerville, the harbor and airport tunnel network shapes east-side reach, and Route 128 (I-95) acts as the de facto outer loop where most suburban retail concentrates. The MBTA commuter rail extends transit-time reach far beyond what driving alone shows, particularly along the Worcester, Providence, and Lowell lines.
Franchise developers should focus on the 128 belt — Burlington, Lexington, Waltham, Needham, Dedham — where suburban income, density, and growth all stack favorably and drive-time behaves more conventionally than inside the city. The Seaport / Innovation District has reshaped Boston's daytime population gravity in the last decade and warrants separate trade-area modeling. Brands should also account for college-town seasonality — Boston, Cambridge, and Somerville together host one of the highest student populations per capita in the country, and trade areas behave measurably differently in summer.