The B186 is a back road through South Essex, running roughly parallel to the M25.
It starts at a maze of roundabouts by Lakeside Shopping Centre, and fights its way through this in a loop south off the A1306, which includes a short multiplex along the A126. Finally heading north, the road clears the A13 (there is no junction here) and narrows down to a more winding country road, though still with two lanes. After passing to the side of the South Ockendon, there's a sharp left and right bend before the road crosses the A127 at a GSJ.
Beyond this, the road climbs uphill through woodland before it meets the outskirts of Brentwood. It then heads back downhill past the station and a junction with the B185, before ending on the A128 just south of the town centre.
The B186 originally started on what was then the A13 (the current B1335) just east of Aveley. When the original Aveley bypass opened c.nbsp;1926, the B186 was extended over the eastern section of the old road to return to the A13 (the current A1306) south of Staveley.
The current route through Lakeside dates from the 1990s, when the shopping centre opened.