Special Report: Walkable Streets

Edinburgh to Enforce 30 km/h Speed Limit on All Residential Streets

With more than three decades of clear evidence, there is no excuse for any city to continue dragging its feet on implementing a safe, humane speed limit for the most dangerous objects on the road.

By Ryan McGreal
Published May 23, 2014

this article has been updated

The City of Edinburgh, Scotland has adopted a 20 mph (32 km/h) speed limit across all residential areas. Around 2,000 residential streets have already been slowed through various traffic calming measures, but the lower speed limit will now also be enforced by the police.

[Councillor Lesley] Hinds said today: "From our research and consultation with residents, we know that there's widespread support in Edinburgh for a 20mph limit in residential streets, shopping areas and the city centre, and we're currently in the process of drawing up further, detailed consultations.

"Lower speeds in residential areas and shopping streets are not just good for safety and environmental reasons.

"Slower traffic makes streets more attractive to residents, pedestrians, cyclists and children, improves the environment for business and enhances quality of life."

The kinetic energy of a moving object is proportionate to the square of its speed. That means if you double the speed of an automobile, its kinetic energy doesn't double, it quadruples.

According to a 1997 British Department of Transport report titled Killing Speed and Saving Lives, a pedestrian hit by a motor vehicle has a 5 percent chance of dying if the vehicle is moving at 32 km/h. At 48 km/h (30 mph) the risk of death jumps to 45 percent, and at 64 km/h (40 mph) the risk of death jumps to a staggering 85 percent.

Edinburgh joins the city of Bristol, England, which officially began implementing a 20 mph speed limit across several large areas of the city earlier this year.

Just this week, Paris, France announced that nearly every city street will adopt a 30 km/h speed limit - and some areas will even have a 20 km/h limit.

These cities undertook studies, conducted pilot projects and are now moving ahead with big, ambitious plans to apply the results of their studies to improve safety and quality of life for everyone.

Meanwhile, in Hamilton, Council would only approve a 30 km/h speed limit in a single neighbourhood - the North End, excluding James and Burlington streets - if it was done as a five-year pilot project with a moratorium on considering speed reductions anywhere else until the end of the pilot.

The first 30 km/h speed limit pilot project was undertaken in the German town of Buxtehude more than 30 years ago, in 1983. Since then, the movement has spread steadily as more and more cities and towns have committed to making their streets safer and healthier for all road users, particularly the most vulnerable.

Today, after more than three decades of clear evidence, there is no excuse for any city to continue dragging its feet on implementing a safe, humane speed limit for the most dangerous objects on the road.

See also:

with files from Nicholas Kevlahan


Update: this article incorrectly stated that 64 km/h equals 50 mph. It's actually 40 mph. RTH regrets the error. You can jump to the changed paragraph.

Ryan McGreal, the editor of Raise the Hammer, lives in Hamilton with his family and works as a programmer, writer and consultant. Ryan volunteers with Hamilton Light Rail, a citizen group dedicated to bringing light rail transit to Hamilton. Ryan writes a city affairs column in Hamilton Magazine, and several of his articles have been published in the Hamilton Spectator. He also maintains a personal website and has been known to post passing thoughts on Twitter @RyanMcGreal. Recently, he took the plunge and finally joined Facebook.

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By Pxtl (registered) - website | Posted May 23, 2014 at 12:14:51

And meanwhile, there's a campaign to get the 400-series expressway speed-limits raised. I'm torn on that one because on the one hand, the fact that everybody is driving 10-20 over is habituating us to be speeders (which is relevant to Hamilton's de-facto 70kph streets), but on the other hand maybe we shouldn't be driving based on what feels safe?

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By Brandon (registered) | Posted May 26, 2014 at 12:02:38 in reply to Comment 101566

Two things here:

1) the environment is radically different. No opposing traffic or cross traffic, no pedestrians, no obstructed sight lines, no sharp corners, etc....

2) by making the speed limits on the highways artificially low where everyone knows you can easily exceed them by 30 km/h and not be at any significant risk, it breeds contempt for city speed limits that are there for a reason. When I see an onramp sign with a yellow advisory limit of 50 km/h that I can easily take at 100+ km/h it makes me question those advisory limits wherever I see them. That being said, if I'm new to the area I always take them seriously until I can make my own judgement because in my arrogant youth I was surprised by signs that really were there for a reason.

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By Ryan (registered) - website | Posted May 27, 2014 at 07:26:23 in reply to Comment 101660

by making the speed limits on the highways artificially low where everyone knows you can easily exceed them by 30 km/h and not be at any significant risk, it breeds contempt for city speed limits that are there for a reason.

Unfortunately, city streets are being engineered the same way, with designs for running speeds significantly higher than the speed limit. As Nicholas Kevlahan put it, "It is no wonder people are speeding on urban streets and treating them like highways - that is how they are designed."

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By mikeonthemountain (registered) | Posted May 23, 2014 at 12:30:53 in reply to Comment 101566

Highways are different. They are primarily for inter-regional movement (longer distances). They are closed environments specially designed and designated for vehicles at high speeds. In my opinion we can raise speed limits on 400 highways to 110kph, just like Alberta, with no ill effects.

Inside the city is where we want to keep a handful of chosen arterials at 50, and make everything else 30kph. Together with encouraging sidewalk patios and nicer public spaces, and the other pleasant features of an urban core.

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By Ryan (registered) - website | Posted May 23, 2014 at 12:26:23 in reply to Comment 101566

maybe we shouldn't be driving based on what feels safe?

Let me turn that around: our streets should be designed so that what feels safe is actually a safe speed.

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By Rod King (anonymous) | Posted May 23, 2014 at 17:54:14

Hi

You can find out about the movement for 20mph speed limits in the UK at 20splentyforus.org.uk

We have over 40 briefing sheets on various aspects of 20mph limit implementation at 20splentyforus.org.uk/briefings.htm

Please contact us for any more information.

rod.k@20splentyforus.org.uk

Rod King

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By kensills (registered) | Posted May 24, 2014 at 09:59:35

50 mph converts to a little over 80 km/h, not 64 km/h as the article suggests. Is the 85% risk of death figure correct for the speed quoted in metric, or imperial?

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By Ryan (registered) - website | Posted May 26, 2014 at 06:19:49 in reply to Comment 101594

Sorry about that. 64 km/h equates to 40 mph, not 50 mph. That was a typo on my part. Thanks for pointing it out - the article has been corrected.

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By epicnorth (anonymous) | Posted May 24, 2014 at 12:27:23

I went to Scotland last year. Edinburgh is mostly cobblestone streets. It would be difficult to go faster than 30km/h without breaking your jaw from the vibrations. I don't know if this city is really comparable to Hamilton.

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By AnjoMan (registered) | Posted May 26, 2014 at 10:12:11 in reply to Comment 101603

And yet when urbanists propose such design choices for our streets, they are opposed because of worries about congestion. So Hamilton can't have slower street designs or speed limits because...people might want to use them?

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By jason (registered) | Posted May 24, 2014 at 22:08:41 in reply to Comment 101603

well then, lets cobblestone all our streets then.

Problem solved.

I'd be happy with abolishing all speed limits if we designed streets that are physically impossible to go more than 30.

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By NortheastWind (registered) | Posted May 24, 2014 at 22:32:28

I'm glad I don't live in Edinburgh.

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By Steve (registered) | Posted May 27, 2014 at 15:07:50 in reply to Comment 101632

I'm gonna go out on a limb here and say likely so are Edinburghians.

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By mikeonthemountain (registered) | Posted May 27, 2014 at 17:27:03 in reply to Comment 101679

The danger of going out on limbs without thinking first, is that they can break underneath you and leave you embarrassed.

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By but (anonymous) | Posted May 27, 2014 at 17:29:08 in reply to Comment 101683

i think he meant that edinburgh is happy that northeast wind doesnt live there...

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By mikeonthemountain (registered) | Posted May 27, 2014 at 17:34:44 in reply to Comment 101684

I read it again, yes of course, my bad, sorry! Leaving my original comment for the link to the article. But I was hit with my own bough breaking (grinning sheepishly :)

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By matthewsweet (registered) | Posted May 25, 2014 at 03:01:42

These cities undertook studies, conducted pilot projects and are now moving ahead with big, ambitious plans to apply the results of their studies to improve safety and quality of life for everyone.

Meanwhile, in Hamilton, Council would only approve a 30 km/h speed limit in a single neighbourhood - the North End, excluding James and Burlington streets - if it was done as a five-year pilot project

Isn't it something at least that Hamilton has embarked on the process? Both this piece and the item on Paris noted that the part of the process in both cities was pilots, and lo and behold Hamilton has a pilot now. Yes I agree the process here is moving at a pace that rivals glacial retreat or perhaps continental drift, since glacial retreat is moving at an uptick lately and our safe streets process is not. But while it sucks that we are so far behind other cities, better that Hamilton is progressing at all than not.

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By Ryan (registered) - website | Posted May 26, 2014 at 06:12:45 in reply to Comment 101639

Both this piece and the item on Paris noted that the part of the process in both cities was pilots, and lo and behold Hamilton has a pilot now.

Other cities conduct one-year pilots in multiple locations, collect and review data, and then implement widely. We're running a five-year pilot in a single location - and reluctantly at that - with an explicit moratorium on implementing pilots anywhere else until after the five years is up.

Why on earth would it take us five freaking years to decide whether it makes sense to reduce speed limits on other residential streets, especially since cities have already been experimenting with reduced speed limits for more than 30 years?

There's a difference between testing an idea prior to full implementation and putting an idea in a box so there's no way it can lead to full implementation.

Comment edited by administrator Ryan on 2014-05-26 06:15:59

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By CharlesBall (registered) | Posted May 25, 2014 at 08:49:37

Speed limits should be just that - limits. People should use common sense and drive within reasonable limits. But the limits need to be reasonable. There is no reason why the limit on the 401 between Oshawa and Montreal should be lower than 130. Why can't the law be that you exceed that and you get significantly punished. Anyone driving even 50 on a side street with parked cars and children is nuts. But Main, King, Queen, Aberdeen, Bay can be 50 no problem. We should have reasonable speed limits and then speed cameras for enforcement like in France. (Reducing the limits to an unreasonably low number turns good people into "law breakers." No one I have seen obeys the new 50 on Main and the 403)

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By notlloyd (registered) - website | Posted May 26, 2014 at 17:06:04 in reply to Comment 101645

The NMA's Model Speed Zoning Law You are encouraged to print and distribute this page. Legislators and traffic engineers would be likely recipients. If they have any questions, they may contact the National Motorists Association (author), 6678 Pertzborn Road, Dane WI 53529. 608-849-6000. Source - http://www.motorists.com/modellaw.htm Statutory standards and requirements for establishing speed limits. Purpose:

Speed limits should represent the maximum safe and reasonable speed on a highway during good traffic and roadway conditions capable of being traveled by the normally competent vehicle operator in a typical motor vehicle. Traffic engineering studies have found that the best way to ascertain the appropriate speed limit is to survey the speeds of free flowing traffic. The speed at which 85% to 90% of the vehicles are traveling at or below has generally been determined to be a limit which minimizes accident risk and maximizes motorist compliance. It blends an optimum combination of efficiency, consensus, enforceability, and safety.

Current statutorily assigned speed limits are characteristically inflexible and based on general approximations or political considerations. The result is that speed limits have become largely irrelevant as a source of guidance to motorists and impractical as a threshold for enforcement purposes. (See the federal study which proves this.)

The speed zoning statute being proposed will overcome the failings and limitations evidenced by current state laws and practices. It provides a scientific basis to establish a uniform and flexible system of speed zoning that will result in safe, reasonable and relevant speed limits. It allows for local roadway and traffic conditions and accommodates changing trends in vehicle speeds. It is further based on the knowledge that the vast majority of motorists are reasonable and responsible people who will comply with properly established speed limits. The following definitions are provided to aid in the understanding of this model legislation. They may or may not coincide with terms and definitions found in related state statutes.

Statutory Speed Limits: Numerical speed limits that apply to various classes or categories of roads (e.g. rural expressways, residential streets, primary arterials, etc.) in the absence of posted speed limits.

Posted Speed Limits: Numerical speed limits noted on signs or other information displays and placed along the roadway corridor to which they apply.

Prima Facie Speed Limits: Numerical speed limits (statutory and posted) that, if exceeded, justify enforcement action. However, if the accused motorist's actions can be proven to be safe, reasonable and prudent for the prevailing conditions, the charge of speeding shall be dismissed by the court of jurisdiction.

85th Percentile Speed Limits: Numerical speed limits based on a scientific survey of free flowing vehicle speeds. The speed at which 85% of the vehicles are traveling at or below is the 85th percentile speed.

Speed Zoning: The process through which proper speed limits are determined and applied.

Speed Zoning Standards:

Statutory speed limits shall be determined thorough valid speed surveys for each road classification. The speed limits shall be set by administrative rule at the 85th percentile speed rounded to the next highest 5 mph increment.

Road classifications for which separate statutory speed limits are to be determined shall include:

Limited access divided highway
Rural highway, uncontrolled access
Urban arterial
Residential

Posted speed limits shall be based on 85th percentile speeds as determined by uniform traffic engineering surveys. Posted speed limits shall deviate from statutory speed limits only if the observed and measured 85th percentile speed differs from the statutory speed limit for that classification of road.

The survey of free flowing speeds by road classification shall be carried out by the Department of Transportation (or equivalent agency). Statutory speed limits shall be administratively adjusted to reflect the 85th percentile speed for each classification of roadway, rounded to the next highest 5 mph increment, no less than once every ten years.

Speed Zoning Procedure

On a five year interval, minimum, each classification of roadway shall be surveyed, using scientific sampling procedures, to determine the 85th percentile speed representative of that classification of roadway. Each survey shall be conducted during clear weather, on straight sections of dry roadway, absent construction, maintenance or visible law enforcement activity.

Speed measurement should be done in an unobtrusive, undetectable manner so as to obtain a sample of normal traffic speeds. If a daytime/nighttime speed limit differential is believed warranted, speed surveys should be conducted during both time periods.

If separate speed limits are believed warranted for large trucks or other vehicle classifications, these vehicles should be the subject of a separate speed survey to determine their 85th percentile speed and subsequent speed limit.

Judicial Standards

The adjudication of speeding violations shall be based on the following standards as related to statutory and posted speed limits:

Vehicle operator may be charged with excessive speed regardless of the numerical limit if, in the judgment of the arresting officer, the vehicle was being operated at speeds in excess of those prudent for prevailing conditions.

The burden of proof is on the officer to document the conditions that required reduced speeds as well as the defendant's failure to drive at speeds that reflected those conditions.

Exceeding statutory or posted speed limits are prima facie evidence of illegal speeding. Evidence entered on the defendant's behalf that proves to the court the defendant was not driving in an unsafe or irresponsible manner shall be considered a valid defense to justify dismissal of the speeding charge.

It shall be an absolute defense in any trial for speeding in excess of a posted or statutory speed limit if the defendant was not exceeding the 85th percentile speed as determined by a valid speed survey for the subject roadway.

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By notlloyd (registered) - website | Posted May 26, 2014 at 17:00:42 in reply to Comment 101645

Lowering speed limits more than 5 mi/h (8 km/h) below the 85th percentile speed of traffic did not reduce accidents. See "Effects of Raising and Lowering Speed Limits" Report No. FHWA-RD-92-084 October 1992 U.S. Department of Transportation Research, Development, and Technology Federal Highway Administration Turner-Fairbank Highway Research Center 6300 Georgetown Pike McLean, Virginia 22101-2296

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By kevlahan (registered) | Posted May 27, 2014 at 09:29:09 in reply to Comment 101665

The key is to ensure the road is designed to make the 85% percentile 30km/h on city streets.

Engineers know how to "retrofit" even wide, fast roads to do this at relatively low cost: add chicanes, crosswalks, parking, narrow painted lanes, planters in the street, bump outs, speed humps etc. There is a big toolbox of options that have all been used for years. City streets should be designed for 30km/h as the 85 percentile speed.

Our freeway speed limit of 100km/h is just bizarre: it is clearly too low and probably should be around 120km/h (or 130km/h reduced to 110km/h in rain or snow as in France) and then enforced rigorously (like in Australia). Currently, even the police drive at around 120km/h, which is 20% over the posted limit. This really does encourage drivers to ignore posted limits. And freeways are designed to be relatively safe at higher speeds: controlled access, barriers between traffic in each direction, no traffic lights, no pedestrians or cyclists.

Comment edited by kevlahan on 2014-05-27 09:30:00

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By notlloyd (registered) - website | Posted May 27, 2014 at 18:22:20 in reply to Comment 101673

and so the tail wags the dog . . .

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By kevlahan (registered) | Posted May 28, 2014 at 10:59:05 in reply to Comment 101688

The engineered speed for a street is just a design choice.

It is not a fact of nature, and we can decide to change our priorities to favour safety for all road users, and to make the streets convenient and comfortable for pedestrians and cyclists, instead of maximizing vehicle speed above all other goals.

And we know how to retro-fit our streets in order to bring down the 85% speed to 30km/h if we want to.

(Don't forget that these streets will also be safer for motorists, and they will make it more comfortable for motorists to reach local destinations. The cost is that driving will not be quite as fast for more distant destinations, but once stop signs, traffic lights and traffic are taken into account the average speed for the entire urban trip would not be that much less.)

Comment edited by kevlahan on 2014-05-28 11:01:02

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By Ryan (registered) - website | Posted May 28, 2014 at 10:18:50 in reply to Comment 101688

Do you mean to suggest that the tail of safety-for-all-road-users is wagging the dog of automobile flow? Because if so, I think you have your priorities in the wrong order.

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By Perturbed (anonymous) | Posted May 26, 2014 at 15:35:52

Comments with a score below -5 are hidden by default.

You can change or disable this comment score threshold by registering an RTH user account.

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By AnjoMan (registered) | Posted May 28, 2014 at 09:29:28 in reply to Comment 101661

Why do we encourage them? and penalize the actual people that pay for the roads and use them legally. Ie licensing and insurance users.

As far as I know, insurance is to pay for damage (to cars and bodily harm) cause by drivers to each-other when they get in accidents...so that doesn't pay for roads. Licensing goes hand in hand with policing, so unless you can show that the proceeds from vehicle registration are greater than both the public expense of policing roadways for driving AND the benefit to policing of having all drivers and their vehicles registered, you can't even say that licensing fees go towards roads. Never mind that in the best case analysis we know that drivers still don't pay for roads.

typical cyclists, they are the least law abiding people using the roads.

Did you ever think that maybe there is a reason why cyclists get away with the things they do? Like maybe because police have realized that it would not meaningfully increase safety, and it would not be worth the money they spent on enforcment?

I would also like to say that as a law-abiding cyclist I take offense to your broad generalizations.

Comment edited by AnjoMan on 2014-05-28 09:29:50

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By banned user (anonymous) | Posted May 28, 2014 at 14:21:40 in reply to Comment 101705

comment from banned user deleted

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By z jones (registered) | Posted May 28, 2014 at 14:35:41 in reply to Comment 101717

This obvious concern troll just screams Allan Taylor. Mods please be advised.

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By wah wah wah (anonymous) | Posted May 27, 2014 at 14:55:14 in reply to Comment 101661

The sad thing is, when this self-entitled asshole inevitably kills someone with their car, the punishment will be a small fine and "here's your license back". Probably end up suing the victim's family for pain and suffering too.

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By Ryan (registered) - website | Posted May 27, 2014 at 06:50:44 in reply to Comment 101661

typical cyclists, they are the least law abiding people using the roads

It makes no sense to allocate road infrastructure based on obedience to the law, since all road users routinely disobey the law.

People riding bikes go through stop signs, ride on sidewalks, ride the wrong way down one-way streets and so on. People driving cars go through stop signs, exceed the speed limit, change lanes without signalling, tailgate and so on. People walking cross the street midblock, cross diagonally, cross against red lights and so on.

The main difference is that people in cars have tremendous potential to harm others due to the mass and power of their vehicles. This is why driving is licenced and regulated to a far greater extent than walking or cycling - not to pay for the roads but to mitigate the risks of driving.

The people who actually pay for the roads are residents, through their property taxes - no matter how they choose to get around. Even if you add up all of the taxes, fees, levies and fines that apply specifically to motorists, they fall billions of dollars short of the total cost to build and maintain our roads.

In addition, automobiles are responsible for nearly all of the wear-and-tear on road infrastructure, dramatically pushing up its lifecycle costs. The government of Waterloo Region calculated that each one-percent shift of trips from driving to active transportation will save the region $30 million in infrastructure costs.

And we haven't even mentioned air pollution from automobiles. In Hamilton, air pollution is responsible for around 700 hospital visits and 100 premature deaths every year, and half of our air pollution is from automobile exhaust.

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By jason (registered) | Posted May 26, 2014 at 22:18:32 in reply to Comment 101661

the 'idiotic bus lane' that carries more people than the other 3 lanes combined?? The only thing idiotic is that we don't have bus lanes city-wide. So much for a free market. We're handing over 99% of the PUBLIC roadspace for the fewest amount of users.

And folks use bikes all year round. More cycle in nice weather of course, but where do you come up with this 'half the year' idea?? This past winter was the worst in 20 years and it was 3 months exactly from our first snowfall till the majority of snow had melted.

Facts are a beautiful thing eh??

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By Pxtl (registered) - website | Posted May 26, 2014 at 16:46:20 in reply to Comment 101661

Stop thinking about what's "fair" as if this was a schoolyard game and start thinking about what's actually sensible policy. If a car is going too fast and loses control, it could kill many people.

If a cyclist rolls through a stop-sign and gets crushed, he wins a Darwin but they don't kill any innocent bystanders - and the only reason that this particular screw-up is so lethal is the cars on the road.

That's why cyclists get a lot more leeway, because they're mostly just putting themselves in danger, not other people. So it doesn't seem "fair" that cyclists get a lax hand from law-enforcement until you consider the difference in the consequences if they screw up.

A car is a far greater responsibility, so it has far greater scrutiny.

And as for the bus lane, remember that it moves as many people as the other 4ish lanes of King put together.

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By Nope (anonymous) | Posted May 28, 2014 at 06:02:04 in reply to Comment 101664

Ah, so it's a double standard, because of "safety". Gotcha.

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By DissenterOfThings (registered) | Posted May 28, 2014 at 08:03:11 in reply to Comment 101701

I don't think you understand what double standard means.

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By Nope (anonymous) | Posted May 28, 2014 at 23:06:53 in reply to Comment 101703

No, I get it.

Standard 1: Cars
- rolling through a stop sign. Doing so can cause injury, possibly death. Police and the justice system punish the driver.

Standard 2: Bikes
- rolling through a stop sign. Doing so can cause injury, possibly death. It's OK though, because they aren't big enough to hurt someone, according to the logic.

I don't get it. Please explain if I'm missing something here.

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By kevlahan (registered) | Posted May 29, 2014 at 09:25:37 in reply to Comment 101747

Since you are asking for an explanation of what you're missing, I'll answer in good faith, since you are clearly confused about relative risks.

You completely mis-stated the potential and actual risk from cyclists and motorists. Motorists kill between 2200 and 3200 Canadians each year and seriously injure between 11,500 and 19,000 each year. http://www.tc.gc.ca/eng/motorvehiclesafe... and this doesn't count the direct and indirect social costs and costs to property.

The danger posed by motor vehicles is clear and well established. And 13% of the deaths were pedestrians and the motorist was found at fault in 67% of cases.

The deaths and injuries to others caused by cyclists are completely negligible.

And it should be obvious why motor vehicles are so much more dangerous: they weigh over ten times as much as a cyclist, typically travel two to three times faster on urban roads, which means they have 40 to 90 times the energy, and they are far more powerful. In addition, motorists have far worse visibility than cyclists.

Yes, the fact cyclists do not and are not capable of causing injury and death to others except in exceptional circumstances does make a difference in how much resources are put into enforcement.

Why should this be surprising? The police also put far more effort into serious crimes than minor crimes, and they tend to ignore some parking violations (e.g. parking on the wrong side of the street, parking in no parking zones on Sundays) because they have more important things to do.

It's not "OK" for cyclists to roll through stop signs, but it is ridiculous to claim that the risk is the same as a motorist rolling through a stop sign, or speeding or running a red light. The fact that "they are not big enough to hurt someone" really does make a difference!

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By Safety (anonymous) | Posted May 28, 2014 at 14:26:18

The roads exist. The science says that you study the road and set the speed limit within the 85th percentile. anything less does not make the road safer. So, when you get the road as safe as it can be, you change the road - why? Because you like things to move more slowly? The obsession with getting rid of private vehicular traffic wags the engineering dog.

My guess is that if studied, the vast majority of city side streets would call for a reduction of top speed to below 40kmph. Many major arteries would be 60Kph or higher in some cases.

Do we need any major arteries? If not, make all the roads side streets and every one drives below 40 KPH. If we need major arteries, leave them alone.

The pedestrian traffic fatality rate, rate being being death ratio-ed to usage, will not drop by any significant factor by simply reducing speed. Therefore, reducing speed in the face of that science means the reduction must be motivated by some other factor.

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By kevlahan (registered) | Posted May 28, 2014 at 16:14:38 in reply to Comment 101718

I'm not sure quite what you are arguing here.

The 85% rule is based on the principle that rules should be aligned as much as possible with actual behaviour. I agree that it is not a good idea to engineer roads for 70km/h and then impose a 50km/h limit. But the 85% rule has nothing to do with safety! The 85% rule is promoted by motorist associations as a way to increase speed limits and avoid traffic tickets, http://www.sense.bc.ca. Note that the belief is that drivers naturally know what speed is safe and so we should just base the limit on their collective wisdom.

But even if this is true (which it is not, the average speed is based on what feels comfortable or what feels safe, not necessarily what speed is actually safe), it ignores the safety of other vulnerable road users such as pedestrians and cyclists. Very few drivers govern their speed by anything other than what feels comfortable for themselves and the American DOT guidelines on the 85 percentile rule makes no reference at all to pedestrian safety (it is also based on some pretty debatable assumptions about human behaviour and risk): http://onlinemanuals.txdot.gov/txdotmanu...

The same argument could have been made 40 years ago to claim that the legal blood alcohol limit should be based on the 85 percentile of what drinking drivers actually measure, because people are good judges about what their own safe impairment level is!

Slower traffic speeds definitely lead to fewer injuries and deaths, both because collisions are easier to avoid because reaction times are longer and because any collisions that do occur are much less damaging due to the far lower energy (increases like the square of speed). This is why, for example, school zones have reduced speeds.

Lower speed limits do not mean less traffic (they could even mean denser traffic), but they will tend to increase the number of pedestrians as the street becomes more comfortable to walk along.

The fact the "roads are there" does not mean the road design can't change. In the 50s and 60s there was a massive campaign of road widening ... they can be narrowed even more easily by adding parking or barriers.

Even in Edinburgh and Paris some major arterial roads will continue have a 50km/h limit, the change is to make 30km/h the default speed unless otherwise justified, rather than 50km/h.

Comment edited by kevlahan on 2014-05-28 16:36:32

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By notlloyd (registered) - website | Posted May 28, 2014 at 17:25:53 in reply to Comment 101726

The 85% rule was based on scientific studies. They were not conducted by motorist associations.(It may be that motorist associations have picked it up but the initial studies were blind studies designed to determine if reducing speed limits increased safety.) What the studies found was that if you have existing infrastructure, reducing speed limits did not increase safety. It says nothing about design. What the studies found was that if you have existing infrastructure, manipulating speed limits has limited impact on the rate or volume of traffic accidents. IOW given a specific road design, reducing speed limits below the 85th percentile will not reduce collisions.

I looked at the data. It is all collisions including pedestrian and cyclist collisions. They observed every type and they are all lumped together. So you are correct, it says nothing specifically about pedestrians.

But there are many factors in road design. Time, and costs are two factors that get marginal attention as people would say just slow down to save lives. The inadequacy of that position is that it ignores the conclusion that slowing down will not reduce death rates - depending upon the specific road in question. I found one study that said that after 10mph, road death rates are not impacted by velocity limits at all. (I will find that study.)

Studies show that danger to any specific pedestrian decreases substantially under 50kmph. So if you take a model human and hit him at 50kph, the model is more likely to die than if you struck him at 30 kph. But an important factor is the Rate. While it appears to be common sense that you should drive more slowly, the fact that higher speeds kill more efficiently says nothing about the rate. So, you need to find out how many pedestrians are killed by drivers driving over 30 kph. Most pedestrians are killed at intersections where driver inattention or pedestrian error are the cause, and not the velocity of the vehicle per se.

If you want to design streets to a maximum speed, say in high density residential areas so that vehicles will not exceed some specific velocity deemed harmful to pedestrians, then you might be correct that the right answer is to design the street so that drivers are uncomfortable driving above that limit.

However, there is no point slowing everyone down if it will not save lives. You can do it for other reasons for sure. But to simply argue that it is to save lives is a bit disingenuous.

A good example is flying in an aircraft. In any individual air crash of a large airliner, the morbidity is likely 100%. It is super dangerous to be in an air crash. But flying is way safer than driving a car based on rates - traveler miles per death. I wager that impairment, driver inattention, distracted driving, jaywalking, dimentia, old age, etc. are far more significant factors in pedestrian fatalities than velocity.

Comment edited by notlloyd on 2014-05-28 17:40:01

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By kevlahan (registered) | Posted May 29, 2014 at 09:33:12 in reply to Comment 101733

Well, the Coroner of Ontario disagrees:

http://news.ontario.ca/mcscs/en/2012/09/chief-coroner-releases-pedestrian-death-review.html http://www.cbc.ca/news/canada/toronto/lo... http://www.therecord.com/news-story/2613...

and he has looked carefully into the statistics of pedestrian fatalities, in particular "among its findings were that two-thirds of the deaths occurred on roads with posted speed limits higher than 50 kilometres an hour, while only five per cent occurred below that limit."

And this report from the American DOT also disagrees

http://www.nhtsa.gov/people/injury/resea...

"Reductions in vehicle speeds can have a very significant influence on pedestrian crashes and injuries. Pedestrians suffer much more serious injuries when struck by high-speed vehicles than when struck by vehicles going more slowly. Also, many pedestrian crashes would be prevented entirely had the vehicles been traveling more slowly, since driver and pedestrian would have had more time to perceive the threat and react to the risk, averting the crash altogether."

The idea that lower speed limits (e.g. 30km/h) combined with road re-design to make it uncomfortable to drive faster does not reduce the number and rate of pedestrian deaths and serious injuries is completely contrarian and not backed up by the actual data. I've quoted the case of Paris numerous times as an example of extremely low pedestrian fatality rate in a City with low traffic speed, lots of traffic and huge numbers of pedestrians. And they are going to 30km/h and 20km/h on all except the major arterials to reduce the injuries and deaths even more.

Comment edited by kevlahan on 2014-05-29 09:39:09

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By CharlesBall (registered) | Posted May 29, 2014 at 11:31:38 in reply to Comment 101775

Interesting discussion.

I think that Mr. K is only looking at deaths. Not accident rates. He is correct on that. The evidence is clear that pedestrian deaths occur far more readily at higher rates of speeds. However, Notlloyd acknowledged that and so appears to agree with the Coroner as well. Notlloyd said, it's like aircraft crashes. The faster a car goes, the more likely an impact with a pedestrian causes the pedestrian's death. But there is more to it than that.

You have to look at rates of death. Not death per speed but death per usage and/or death per usage and speed (or even more complex variables.) I would add that you also have to look at the sample size and shape as well .

Let's say that there are 10 pedestrian deaths in Hamilton per year on average. If you reduce the speed limit to 30kph given the current road construction, the science says that every year going forward, provided that the current average death rate is largely consistent and the norm, you will continue to have 10 deaths per year going forward (kid running out between parked car, demented person walking out into traffic, drunk driver speeding, teen on cell phone not watching, something like what has happened at queen and Main this year etc. etc.) Plus, people will not obey a blanket 30kph speed limit without major re-engineering.

Now, if you then spend several hundred million dollars and rework the roads to force drivers to reduce speed so as to comply with the 85% rule, you then need to be able to estimate the death rate and determine if it should be done.

Given that the accident rate is unlikely to change significantly (people will still be hit and injured) the question then becomes, how many deaths can we prevent. Is it 5 (50% reduction)?

The City is very large with different types of neighbourhoods. Some of the recent death in Hamilton occurred on major arteries on busy roads at higher speeds. Some occurred at intersections at lower speeds. One lady died who seemed to be fine and likely died because she was elderly and simply fell. Do you have to re-engineer all roads?

Maybe we need to look at where the deaths occurred and look at each part of the city separately. What if the data is that all of the downtown death are already occurring at speeds below 30k and all of the out of downtown death are at above 50K. Do you leave the downtown alone and re-engineer everywhere else?

What if the deaths are random? The actual numbers are not very large. They are far lower today than they were 50 or 75 years ago. Maybe all the engineering in the world will accomplish nothing vis a vis the death rate.

I can’t imagine anyone obeying a 30 kph speed limit on Fennell, or Upper Gage or Mohawk. Maybe they would on Concession (where hardly anyone drives 50kph anyway.)

I think one of the reasons that the Mountain subdivisions north of Mohawk were designed the way they were was to eliminate through traffic and reduce speeds. Hardly anyone can do 50kph in those neighbourhoods and I don’t hear any clamouring from the residents up there for reduced speed limits.

I think what Notlloyd is saying is that it is more complex an issue than simply reducing velocity.

Velocity is a factor in 100% of accidents. So the only way to eliminate accidents is to eliminate any traffic. If the goal is to eliminate pedestrian collisions, you must eliminate traffic.

This all begs a horrible question; how much money do we spend to save five lives?

People want simple answers and simple solutions. However, sometimes the most obvious solution is not the best solution. A blanket reduction in speed limits may actually increase the problem if the 85% rule is true (the corollary is that people’s behaviour being what it is will be such that people will not obey rules they think are wrong.)

Comment edited by CharlesBall on 2014-05-29 11:34:01

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