Understanding Seattle's geography
Why Seattle's drive times defy radius math.
The two Lake Washington bridges are the controlling constraint for every east-west isochrone in the Seattle metro. A site in Capitol Hill has a fundamentally different reach into Bellevue than a site in the U-District, simply because of bridge proximity. Puget Sound erases the western half of any waterfront trade area, and the north-south topography squeezes I-5 into a chronically congested spine. Ferry routes (Bainbridge, Kingston, Vashon) add a small but meaningful population that drive-time alone won't capture.
Retail teams should treat the Eastside (Bellevue, Redmond, Kirkland, Issaquah) as nearly an independent market — household income there is among the highest in the country, and the Microsoft/Amazon employment footprint creates daytime population concentrations that warrant separate trade-area templates. Bridge-peak congestion can swing a 20-minute polygon by 40% between AM and PM, so dayparted modeling is essential. Brands sensitive to weather should also account for Seattle's wet-season trip suppression, which is real but smaller than commonly assumed.