San Diego is a city of mesas and canyons, and the freeways run along the flat tops and down the valleys between them. I-5 follows the coast from the Mexican border at San Ysidro through downtown and up through La Jolla toward North County. I-805 parallels it inland, I-15 runs north from the mid-city area through Kearny Mesa and Mira Mesa toward Escondido, and I-8 heads east from Mission Bay through Mission Valley toward El Cajon. SR 163 runs through Balboa Park, SR 94 heads east from downtown, and SR 52 crosses from La Jolla to Santee.
Rush hour bottlenecks form where the freeways merge. The 5 and 805 merge near Sorrento Valley is slow every weekday, I-8 through Mission Valley fills during events and commutes, and the 15 through Kearny Mesa is busy most of the day. The Coronado Bridge rises high over the bay, and border crossing lines at San Ysidro and Otay Mesa mean long idles. A car that overheats in one of those backups is a common reason for a mobile repair once it's moved somewhere safe.
San Diego International Airport sits on the bay just northwest of downtown, close enough that its parking lots are an easy trip for a mechanic. The Trolley connects downtown with the border, East County, Mission Valley and UC San Diego, and the Coaster runs up the coast. The Navy and Marine Corps are a big part of daily traffic, with bases at Naval Base San Diego, North Island, Point Loma and Miramar generating heavy commuter flows.