How Do Speed Limits Combat Pollution?

The Welsh government has signalled its intention to introduce temporary speed limits on five major thoroughfares in the country in an attempt to ease congestion and bring down pollution levels. The government has come under pressure from the High Court after it exceeded EU thresholds for air pollution on multiple occasions.

Projected to cost a total of £20 million, the initiative will introduce temporary speed limits of 50mph, with a view to the limits being made permanent if the schemes are effective. It’s hoped that they will help to reduce nitrogen dioxide (NO2) emissions on the roads in question, which have been identified as pollution hotspots in the past.

Where Wales is falling down

Although no Welsh monitoring stations recorded “very high” levels of nitrogen oxide (NO) in 2016, there were 70 days of “moderate” pollution and one day with “high” levels of contamination. What’s more, five different stations exceeded annual limits for NO2 concentrations.

The most concerning of these was the A472 Hafodyrynys Road, nicknamed the most polluted road in the country, which broke the hourly mean threshold NO2 levels on 60 different occasions, which is 42 more times than EU legislation allows.

As a result, air pollution has become the second biggest priority for Public Health Wales (behind smoking) and is thought to directly cause the premature deaths of up to 2,000 Welsh people every year.

Putting the brakes on pollution

The Welsh government has been under pressure to improve air quality and reduce transport-related pollution for some time, and in February the High Court commanded ministers to put in place a plan of action by the end of July.

In response, the government has announced it will introduce temporary speed limits of 50mph at five different spots across the country, effective at the beginning of June. The stretches of road in question are:

• A470 between Pontypridd and Upper Boat
• A483 at Wrexham
• A494 at Deeside
• M4 at Newport
• M4 between at Port Talbot

It’s hoped that by slowing down the traffic moving along these busy pollution hotspots, the authorities can ease congestion and thereby reduce the amount of emissions from passenger vehicles at peak times of travel. Travelling at a constant speed, rather than alternately accelerating and decelerating, can be far better for the environment, as evidenced by recent attitudes towards speed bumps in the UK.

Not everyone convinced

However, the government’s proposals have been greeted with disappointment and scepticism from some quarters. Opposition party Plaid Cymru has called the amount of time it has taken for the government to react “shameful”, while ClientEarth, the environmental law firm which took the case to the High Court in the first place, has said it will be “scrutinising these draft proposals to uphold people’s right to breathe clean air across Wales.”

Meanwhile, the RAC have cast aspersions on how effective introducing a speed limit will be at all. “Slowing down traffic can help to improve flow, but if there are simply too many vehicles for the road space, then jams are still likely to occur so this is as much a question of capacity as anything else,” commented Nicholas Lyles, head of road policy at the RAC.