Paths for posteriors
An assessment of Edinburgh’s cycling infrastructure
Last week I was trundling down Leith Walk’s infamous cycle lane and realised that I was having a deeply unpleasant time.
It’s wasn’t the ongoing threat of HGV drivers mounting the kerb, or drivers blasting through STOP signs at the junctions, or having to swerve around the pedestrians squeezed into the cycle lane by the preposterously narrow pavements.
No. It was the dreadful surface quality. Despite a warning from Spokes, the cycling advocacy group, the entirety of this critical active travel route has been hand laid, meaning that while drivers enjoy a beautifully smooth surface on the carriageway, cyclists have to put up with buckarooing their way down the Walk.
This was something that worth quantifying, in the hope that the same mistake won’t be made again. Deploying the in-built accelerometer on my phone, I set out to test the primary cycle corridors in the city. I used the busy North Meadow Walk (NMW) as my baseline; it has a good surface, with a few bumps and rough patches.
Roughness
On NMW I recorded a low median figure— that is, the middle number in all the observations my phone made as I cycled along. I think this is the best way to measure the general condition of the surface as it is not as affected by the very large bumps that come with potholes and other aberrations.
The paths of the north Edinburgh path network, or NEPN, tend to be the smoothest in the city. The new city-centre-west-to-east-link (CCWEL) is also of good quality on this measure.
Bumps
“Bumps” are how I describe the fluctuations in the surface that can make life miserable for cyclists. To capture the size and frequency of such bumps, I calculated the 95th percentile of recorded acceleration for each of my journeys in Edinburgh. That is, the value at which a particular bump will find itself in the top 5% of all bumps for that particular path.
The same sequence of paths appears, though this time CCWEL doesn’t perform quite as well.
Very large bumps
These are the sort of thing that can throw you from the saddle, or knock your panniers off. The 0.999 quantile.
The most severe bumps are found on Leamington Walk, with the Innocent Railway Path also suffering from a particularly awful surface on this measure. CCWEL scores very well, while on-road cycle paths typically do worse.
Overall score
I gave equal weighting to each of the three measures described above and found that the worst surface you can find in Edinburgh is on Leith Walk’s northbound cycle lane. No surprise.
This was followed by those on McDonald Road and the direct route between Kings Buildings and central campus of Edinburgh University. The worst paths tend to be those that encounter heavy vehicle traffic, or were constructed some time ago.
That makes the brand new cycle-only paths on Leith Walk, Picardy Place and outside Toppings particularly woeful.
Focus on Leith Walk
I also cycled down the carriageway of Leith Walk and found that for all three of my measures, it’s significantly better than the adjacent cycle lanes.
Map of largest bumps
The most severe bumps have been plotted on this interactive map.
Methodology
I used a google pixel phone, quadlock phone mount and the Physics Toolbox app to measure acceleration as I cycled along, measuring linear acceleration and recording my position via GPS.
I used the square of acceleration in this analysis on the assumption that discomfort does not correlate 1:1 with acceleration.
My phone made roughly 50 observations per second; after data cleaning, I had nearly half a million observations to play with.
Caveat — my phone isn’t the best measurement tool in the world, and the statistics I have contrived aren’t perfect either. However, I assert that they will be consistent with the experience of most cyclists in Edinburgh.