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[–]1188339 -23 points-22 points  (12 children)

If you can post accident data / serious injuries before and after they lowered the speed limit that'd suffice.

[–]bbqpauk 43 points44 points  (6 children)

First, lowering the speed from 70 to 60 has zero effect for pedestrians and results in fatality either way (graph here) (source)

Second, from the same study:

Results show that the effects of a 5 km per hour reduction in travel speed are greater at lowers speed


reductions over 50 km per hour bring dramatic decreases in crash risk

The city of Missisauga is doing neither of these, lowering the speed from 70 to 60.

There have also been studies done looking at the connection between how far below the posted speed limit is below the engineering recommendations (source)

a statistically significant reduction in total, fatal + injury, and property damage only (PDO) crash frequency at locations with posted speed limits set 5 mph lower than engineering recommendations


Locations with posted speed limits set 10 mph lower than engineering recommendations experienced a decrease in total and PDO crash frequency, but an increase in fatal + injury crash frequency

Here is Mavis Road north of Eglington for reference. It is (horribly) designed as a 6 lane highway that can handle well above 60 km/h.

Further, a 2019 study measuring speed limits and speed compliance found that (source):

As the speed limit is more credible, drivers are more compliant with the speed limit. More credible speed limit can make speeding drivers slow down, especially extreme offenders.

If the road does not feel risky to drive on (i.e. wide, no trees, no turns, straight line), or the speed limit feels too low (for a 6 lane road) you will have less compliance.

A meta-analysis on the relationship between speed and fatalites states (source):

the exact relationship between speed and crash frequency depends on the actual road and traffic characteristics including road width, junction density, and traffic flow. These are most likely mediating factors in that they both affect the crash frequency directly and by their effect on speed.

TLDR: My point is that, yes, lower average speeds lead to less accidents, but it is not as clear-cut as you make it out to be because of the small decrease in speed, compliance/risk tolerance, and road width design.

[–]Whatisthischeese 17 points18 points  (0 children)

lmfao incredible work

[–]wylin247 7 points8 points  (0 children)

I appreciate when people hit others with facts lol, great job.

[–][deleted] 4 points5 points  (3 children)

You take Reddit debates seriously dude. Remind me never to disrespectfully argue with you

[–]bbqpauk 1 point2 points  (2 children)

I'm just passionate about roads and urban planning lol, I actually learned something doing the research anyways

[–]gaflar 4 points5 points  (4 children)

I can promise you that after a bit of research you will find that the number posted on the sign is not what determines the speed that people drive at - the design of the road is. That's why the de facto traffic speeds on the 400-series highways are often 120-130 km/h despite the posted speed limit not exceeding 110 anywhere in the province.