Road transportation in Ajax is dominated by Highway 401, which runs east–west through the town, dividing it in half. Access to Highway 401 both east and west is available via Westney Road and Salem Road. Only four streets allow transportation from the north end of town to the south end of town by crossing over or under Highway 401. These streets are (from west to east) Church Street, Westney Road, Harwood Avenue and Salem Road. Lakeridge Road crosses the highway, but it is traditionally held to be the border between the towns of Ajax and Whitby. Notable streets that run parallel to the highway are (from north to south) Taunton Road, Rossland Road, Kingston Road (Highway 2) and Bayly Street. At Salem Road is where Highway 401 narrows to three lanes each way, causing a severe traffic bottleneck eastbound during rush hours and special holidays due to increased travel to Ottawa and Montreal.