...a hill a car can drive up or down
...officially marked with a road sign
...within Greater London
I think it's Downe Road in Cudham, which I blogged about yesterday.
Having scoured an Ordnance Survey map of the capital, it seems to be the only hill inside the Greater London boundary to be marked with a double chevron.
<< means gradient steeper than 20% (1 in 5)
< means gradient 14% to 20% (1 in 7 to 1 in 5)
But OS maps only show chevrons on 'important' roads, so triangular warning signs are probably a better indication of a steep hill. Official guidance states that these signs should only be used where the gradient is 10% or more.
Here's my attempt at a list of the steepest roads in London. I've found a 1 in 4, a 1 in 5 and a 1 in 6, each with a sign. Can you help me find some more?
Downe Road careers downhill from Cudham Lane, specifically from the road junction nearest the parish church. It drops sharply to a second junction (with Church Hill) before bending left and heading down the steepest hill in London. A further right-hand bend aids the descent to the valley bottom, the road now narrow enough to make the speed limit of 40mph look somewhat unwise. One of yesterday's commenters, BCW, describes the act of cycling in the opposite direction...
Cycling from Downe to Cudham is 'fun' - a long, winding downhill run into the valley, then lots of uphill, steadily getting steeper up to that killer 1 in 4 section at the end where, if you aren't careful, your front wheel can come off the ground!
Church Hill is also steep enough to merit a chevron on the Ordnance Survey map, but only one, not two. Indeed if you stand above the road junction (pictured above) it's plain to see that Downe Road (right) descends faster than the 'gentler' lane to Berry's Green (left).
20% (1 in 5) Fox Hill, Crystal Palace(Bromley/Croydon) [map]
This one's not on the Ordnance Survey map because the road is too minor, but Fox Hill is definitely steep because a sign at the bottom says so. It's also a historic track, and was immortalised in oils in 1870 by the French impressionist Camille Pissarro (who was living in Norwood at the time). The road rises gently at first, past some fine Victorian villas and a small recreation ground, before gaining in oomph up a steep, intense climb. Most residents in the houses alongside park facing downwards for an easier getaway. At the top of the 1 in 5 bit is a old parish boundary marker, then Fox Hill peters out at Church Road, atop the heights of Crystal Palace.
17% (1 in 6) Ena Road, Pollards Hill(Croydon) [map]
Pollards Hill is an actual hill on the boundary of Merton and Croydon, with panoramic views over parts of south London from the park at the summit. Most of the surrounding slopes have been built upon, including a grid of suburban avenues on the northern flank, one of which is Ena Road. Drive in at one end at it doesn't look too bad, but approach via Norbury Cross and a triangular sign warns of a very steep gradient just round the bend. What follows doesn't disappoint, if somewhat innocuous in its setting. White-fronted semi-detached homesteads rise to either side, the gable of one at first floor window height for its neighbour. Within 100 metres you've ascended 17 metre (which should be obvious given how gradients work), and can now gaze back across the vast vista now opened up above the rooftoops below. Beyond a flat summit Ena Road then dips more gently down... but all the finest freewheel/skateboard action must surely be on that western side, so long as you mind the sharp right-hand bend at the bottom!
Remember, this is an empirical list... so if you can't provide proof (e.g. a chevron on a map, or a snapshot of a sign) then it doesn't count.
Remember, only roads with a triangular sign are eligible... so, for example, Swains Lane past Highgate Cemetery is infamous as a steep climb for cyclists, and has a maximum gradient of 14%, 18% or 20% depending on who you believe, but it doesn't have an official sign at the bottom, so it doesn't count.
Remember, only roads in Greater London are eligible... so, for example Succombs Hill in Warlingham is infamous as a steep climb for cyclists, and has a maximum gradient of 25% according to the sign at the top, but Warlingham's just outside Greater London, so it doesn't count.
Remember, these are official gradients... so, for example, a bike app or GPX file which shows a gradient of 23% may only apply to a very brief section of road, so isn't what a triangular sign would say, so doesn't count.