lower speeds on Oxford's ring-road

The speed limit on Oxford's ring-road should be reduced to 30mph where there are significant at-grade crossings (such as at Barton Park, Kiln Lane) and reduced to 40mph where it passes housing (past Rose Hill, Littlemore, Wood Farm, etc.). This would help with road danger, community severance and barriers to walking and cycling, and with noise pollution, but also with air pollution, vehicle collisions, and carbon emissions.

After five months, the results show consistent improvements across traffic flow, 
safety, and environmental impact.
Traffic and flow:
 – 16 percent reduction in congestion, with fewer and shorter traffic jams
 – Smoother traffic flow and a slight increase in average daytime speed
 – Travel times remained virtually unchanged
Traffic safety:
 – 17 percent fewer accidents
 – Lower speeds led to fewer and less severe collisions
Environment and noise:
 – 12 percent reduction in nitrogen dioxide (NO₂) levels
 – 6 percent drop in particulate pollution (PM₁₀)
 – 2.6 decibel reduction in traffic noise, especially at night
Traffic volume:
 – Only 2–3 percent fewer vehicles on the ring road
 – No significant diversion to surrounding roads

• Lower speeds would mean fewer vehicle collisions and less serious ones, which would reduce deaths and serious injuries and also reduce congestion resulting from collision-driven road or lane closures.
• Lower speeds would make at-grade crossings safer and more accessible. There are obvious examples at Barton Park and Kiln Lane, but there are many less obvious crossings at-grade whose safety and usability would be greatly improved by lower speeds. It is notable that the Wolvercote and Cutteslowe roundabouts and the A40 between them already have 30mph speed limits.

• Lower speeds would significantly reduce noise pollution and its adverse affects on health. This would benefit large areas of the city, since background noise from the ring road extends a long way, but would particularly benefit areas such as Rose Hill, Littlemore, Wood Farm and Barton, which are among the areas of Oxford with the poorest health.

• Keeping speeds below 50mph would reduce carbon emissions and air pollution.

Enforcement of the existing speed limits would help. Measurements at Barton Park found nearly half of all vehicles on the A40 exceeding the 50mph speed limit (the average speed was 49mph).