Edinburgh is proposing a significant increase in the number of streets covered by 20mph. This is being promoted as a way to encourage waking and cycling and to improve road safety. It has been reported that they also support the scheme because ‘lower speeds make people feel safer when they are walking and cycling and make streets better places to live’. I am very supportive of 20mph zones, I live in one myself, and they do indeed help make streets feel less intimidating. However.. it is also very clear that 30 mph speed limits are being retained on the roads where most people are getting injured.
Here are three maps to show the compromises being taken between road safety and ‘keeping traffic moving’. The first map shows the proposed streets to be 20 mph (green and yellow) and 30 mph (blue). The second map shows where people have been injured between 2000 and 2010 by mode (blue for pedestrian, red for cyclists, tan/green for vehicle occupant). The final map shows these two superimposed illustrating that very few crashes from the past 10 years have actually occurred on the roads included on the scheme. (Click on maps for full size versions)
Existing 20 mph zones (green) and proposed schemes (yellow)
Location of traffic casualties by mode in Edinburgh 2000-2010
Overlay, traffic casualties 2000-2010 on top of proposed speed limits
One realistic approach for now might be to welcome the introduction of these 20 mph limits in residential areas and also to also press for average speed camera checks on the remaining arterial roads enforcing the 30 mph limit as they have just installed in part of Plymouth.
Pedestrian Liberation 
If you look at where the student halls of residence are (holyrood road, blackett) and the two main sites (George square and west mains), there is no way to cycle from the halls of residence to either university site without going on 30mph roads for most of the distance.
I got doored once on Ratcliffe Terrace heading between the two campuses; I switched to the slower back roads west of there. But even those back roads have 30 mph proposals. This is ridiculous. Every road in the zone that goes anywhere is 30mph
compare with bristol where all but the Mway and a couple of others were kept above 20 mph.
http://www.betterbybike.info/inner-east-bristol-20mph-speed-limit-comes-into-effect
Even there, the city centre to lawrence hill route could have been lowered, just to gradually slow down cars coming off the M32 to urban speeds.
Great application of maps! I wish I had had access to these maps when the consultation was in process as they show clearly the point I was trying to make. It would also be interesting to over lay a map of population density, as there are large numbers of people who live in the tenements along the atrial routes. The quality of life of these people is being sacrificed for the convenience of those living outwith the city and who commute in by car.
Off topic but have May-Gurney ever got back to you?
Not yet. I have been wondering what to do with them! Any ideas?
Did May-Gurney do the work? If so, why did they need the signs if they were able to do it without. If not, then was the work really required and were the signs really required?
Sorry, I know this is O.T. but it intrigues me.
Great maps.
I agree with Kim, about how interesting it would be to look at population density. I think the other interesting factor would be vehicle density. Your is showing most accidents happen on main road which may have the highest numbers of vehicles, cyclists and pedestrians.
Agreed, but looking at it another way round it is exactly these places with high densities of people and vehicles that should get the safety treatment. Is it enough to say ‘we are only killing 0.01% of people who go down this road, or should they be saying ‘we kill nobody’.
Looking at it crudely, there are probably two ways people die on the road, one is by being hit, normally by a vehicle traveling at speed, the other is by being flattened under a lorry. Average speed cameras should be pretty good with the ‘being hit at speed’ ones, for the flattened ones we need some serious redesign of lorries.
What I would like to see is some police speed survey results for the relevant streets. The police often do surveys and you may be able to get the results. If you can get them then let me know and I will see what we can do with them. Here are what Cambs Police publish
http://www.cambs.police.uk/roadsafety/speed_surveys/survey_results.asp
Also, I found this local company that does surveys.
http://www.traffic-data-collection.co.uk/speed-surveys.html
There are some results in this report actually:
http://www.edinburgh.gov.uk/download/meetings/id/32958/item_23-south_edinburgh_20mph_limit_pilot-response_to_traffic_regulation_order_consultation
It shows that there are 12K vehicles per day on this road with an average speed on 26.8mph and 15% of vehicles are exceeding 33.8mph. On most roads 15% of vehicles are exceeding 33mph. These are not the arterial however. Are they faster and busier?
Kilgraston Road
26.8mph
33.8mph
9,445