From a lit town centre to the dark side of the park
Morden town centre is dominated by buses, with stands, stops and pedestrian crossings along London Road, and it is well lit for all of them. Drive a mile in almost any direction and the picture changes. Bishopsford Road runs through the St Helier estate past Imperial Fields, Morden Road skirts Morden Hall Park on its way towards Mitcham, and the long residential avenues of the estate have trees, traffic calming and parked cars but not much in the way of bright lighting. That is where you find out what your headlamps can do.
A lens that has gone milky or amber is scattering its light instead of projecting it, so the beam loses its defined cut-off and the road ahead flattens out. The effect is particularly unhelpful at a busy multi-exit junction like the Morden Hall roundabout, where St Helier Avenue, Morden Hall Road and Morden Road all meet, because judging a gap depends on picking up an approaching car's position cleanly. It is also unhelpful on an evening at Imperial Fields when everyone is leaving at once.
The cause is simple and nothing to do with the bulbs. Polycarbonate lenses carry a thin ultraviolet hard coat from the factory, and heat from behind, sunlight, motorway grit and harsh cleaners all wear it thin. Once it fails, the plastic underneath oxidises. From around five to eight years of age it starts to show, sooner on a car parked outside, which covers most of the estate. Fitting brighter bulbs behind a hazy lens only increases the scatter and the dazzle.
We assess the unit first and rule out internal faults, then mask the surrounding paint and trim, wet sand through progressively finer grades, machine polish, apply a UV-stable clear coat and check the beam pattern and aim. The route is Morden Road east past Morden Hall Park into Mitcham, then Cranmer Road and Carshalton Road south past Mitcham Junction, around 12 minutes. The coating needs curing time, so we will tell you at booking whether to leave the car.