Tonight we welcomed Dr Lee Woods from University of Portsmouth who gave a very interesting talk on the evolution of road design over the decades. Lee took us on a virtual tour, explaining how traffic designs and standards have changed, with real examples from our very own city.

We looked at Bath Square in Old Portsmouth as an example of streets in the time before design standards. Bath Square has active frontage with windows and doors facing the street, horizontal alignment (it’s a curvy road), minimum road width, minimum building setback and a textured road surface. Traffic speeds are low and probably most people feel safe walking here, albeit the cobbles might cause issues for some.

Next we went to Marmion Road in Southsea, which is a bit more modern, with smooth road surface, and the street is a bit wider. There are mixed uses of the buildings. There is on-street parking which has pros and cons, slowing down some of the traffic, but blocking people from crossing wherever they would choose. The collision record looks fairly low compared to other areas in the city.

We then looked at the seminal work by Colin Buchanan called Traffic in Towns. This work from the 1960s proposed separating out both land uses (residential, industrial, retail) and road users, with large highways, bridges and underpasses for people walking. Milton Keynes was the best example of this in practice but Estela Road and the M275 entering the city to Portsmouth show similar features with high rise buildings with elevated walkways and no active frontage. This was the underlying principle of Portsdown Park in Cosham, which has long been demolished. Anglesea Road and the St Michaels Gyratory by the University are further historical examples of trying to separate out people walking and cycling from traffic.

We discussed the Predict and Provide policy that supported a massive road building project in the UK in the 1980s and 90s. It was, and still is, very flawed. Providing more road space does not make travel easier or quicker. It just means people can travel further, and more people are attracted to drive.

Anchorage Park is a classic 1980s car-oriented development - sometimes described as dead worm design, speaking to the shape of the roads within the estate. It’s fine if you drive, it’s very easy to get about. There are wide roads, with fantastic road surfaces. If you want to walk or cycle, you have to travel further than if more cut-throughs had been considered. There are fewer active frontages, and lots of tall garden walls (enclosing rear gardens), so it can feel less safe.

Our next stop was the junction of the Esplanade with St George’s Road at the seafront. This would have been built to an earlier version of the Design Manual for Roads and Bridges, which today wouldn’t be applicable to a location like this, only much bigger and busier roads. The requirement of that guidance (to get as much traffic through the junction as possible, and the sight lines to support that at about 15m back from the junction) make it horrible for walking and cycling. The zebra crossing has had to be moved away from the desire line, and crossing east to west means walking across around 30m of asphalt, when it could be reduced to more like 6m and still work perfectly well for drivers.

Festing Road was our next stop, where we looked at changes to junction design over time, where the traffic lanes have reduced in width, as space for people walking has increased. Good job.

In the mid to late 1990s, coming full circle - Home Zones came along, and Cumberland Road off Queen Street is a good example of this, with pinch points, changes in road texture, and lots of planting, to make the roads safer. New design guidance at that time, called the Manual for Streets, was also in this vein - slow down the traffic, reduce the visibility splays, and prioritise people walking. The Milton area, and in particular Cotton Road, was given as a good example of this. The visibility at junctions is around 2.4m so you have to be much closer to the junction before you can see what’s around the bend, which forces people driving to slow down.

Finally, Lee shared the highlights of the work of one of his PhD students which showed that lower visibility splays really do help to reduce collisions on the minor arms of three arm junctions.

Lee summarised this history of engineering by saying, even as a traffic engineer he would admit that, if you have to introduce a lot of engineering into a location, you’re really admitting that you’ve failed in your original design. The buildings, streetscapes and road layouts should be able to do this from the start.

And, finishing on a lighter note, Lee shared a video of a green wave in Denmark, on a route where the traffic lights are timed so that people cycling, providing they maintain their average speed, following green lights on the road surface, can get through all the traffic lights on green!