The B115 ran from Hackney to Leytonstone in East London.
Starting on the A107 Mare Street the road headed east along Victoria Park Road to cross the B113 and B114 at the northeastern corner of the park itself. The road then followed Ruckholt Road across the Hackney Marshes to reach Leyton, where it zigzagged across the A112 High Road. It followed Grove Green Road to enter Leytonstone and crossed the railway line by Leytonstone station to join Church Lane, which it followed to its end on the A11 High Road.
When Eastern Avenue opened in 1924, the B115 was improved and upgraded to class I status, in order to bypass the A11 through Leytonstone and Stratford, becoming the A106 west of the A112, with the remainder of the road gaining that number much later. Although the ex-B115 remains the A106, the arrival of the A12 in the area has caused the original route to be extensively diverted around Leytonstone, with the old route across the railway line now severed and Church Lane unclassified.