The Ontario Highway Series is about present and former highways which made up the provincial highway network. Some of these highways still exist within the provincial highway system but many of them or portions thereof have been downloaded to lower tier municipalities. This former highway is a bit of an exception as it is now located entirely within the city limits of London. It formerly existed in the County of Middlesex and the City of London.
Highway 135 was a former highway in the City of London running from Highway 401 in the east to highways 2 and 4 east of Lambeth. Highway 135 served a a route between highway 401, connecting to highways 2 and 4 providing a corridor to Lambeth from the 401 and in conjunction with highway 2 to highway 81 and via highway 81 northrly to highway 22 via Strathroy, with highway 22 providing a route westward to Sarnia in the days prior to the opening of the multi-lane 402 between London (Highway 401) and Sarnia.