The road appeared to come to Streatham’s rescue last Thursday evening, apparently providing more capacity for southbound vehicles than was available on a debilitated Streatham High Road.

Thames Water had yet again disrupted traffic flows on that section of the A23, installing temporary lights to reduce the road to a single shared lane for both directions.

Traffic briefly threatened to build up in the afternoon, with northbound queues to the St Leonard’s junction trailing back to Tesco and the leisure centre at around 4pm. But issues appeared to resolve themselves, and journey time data revealed no significant delays on the buses in the peak of the rush-hour.

The lane closure limited southbound rush-hour vehicle flows on the High Road to around 400 per hour. But on Valley Road, southbound flows exceeded 450 vehicles per hour, according to spot counts carried out by StreathamStuff.

The numbers indicate that Valley Road – which a Labour-led council may yet plan to close again to through-traffic, despite the failure of the Streatham Wells LTN last time it was closed, two years ago – plays a key role in Streatham’s transport network, especially when there is disruption elsewhere.

StreathamStuff noted 135 vehicles travelling south past the designated counting-point on the High Road*, including 22 buses, in a 20-minute period from 5.30pm.

That’s not much more than half the maximum flow rates for the road, when it’s fully open, and busy but flowing – even on Saturday lunchtime, with the roadworks finished, the number was in the 170s. But it’s about 50% more than when near-gridlock struck Streatham’s rush hour, when the LTN was in place in 2024 and traffic counts sank rapidly as congestion increased.

On Valley Road, a 20-minute count at 6.30pm noted 155 vehicles (including one bus) arriving southbound at the roundabout junction with Gleneldon Road.

Campaigners – originally for a “Safer Valley Road” and more recently under the banner of Liveable Streatham Wells – have long said that such volumes are too high for a relatively narrow, “residential” street like Valley Road, and that the traffic needs to be tamed and reduced, including to allow more and safer cycling and walking.

But the effects of the LTN seemed to show that shutting Valley Road – precisely because its traffic volumes are so high – not only removes a key pressure valve for neighbouring “main roads”, but also simply displaces more traffic than they can handle.

Critics of the old LTN – which Labour appears to want to bring back, once work has finished on the A23 at Streatham Hill – point to the classification of Valley Road and neighbouring Gleneldon Road as “distributors”, and argue that they effectively are main roads themselves, and just too big to close down.

*Outside the window of The Holland Tringham