How we could build roads for fallible humans rather than 'perfect operators'

"It's not that historically we didn't value safety; it's just that we were relying on individual users to be perfect operators, which isn't realistic."

Compromises need to be made between form, function and cost

Calgarians on foot, in cars and on bikes are all trying to get to the same places. But how do you build roads for everyone? (Evelyne Asselin/CBC, David Bell/CBC, Robson Fletcher/CBC)

This story was originally posted on Oct. 3.

Share — it's the mantra we've been told to recite since we were in diapers. But whether you're a motorist, cyclist or pedestrian, you've probably seethed at some point over exactly how we share (or don't) on the road.

Sometimes it feels like two-year-olds share cookies easier than Calgarians share their roads.

But when you force conflicting interests into a common space, you get impatience, distraction and frustration — and, at worst, deadly consequences.

The designers of our roads, therefore, have to somehow juggle the interests of motorists (who want to drive quickly and unimpeded), pedestrians (who would prefer not getting run over when they cross the street) and cyclists (who neither want to be impeded by pedestrians, nor run over by motorists).

"The inconvenient truth that nobody likes to hear or say is that safety is an economic issue," says Alex de Barros, associate professor in the department of civil engineering at the University of Calgary.

"We're trying to balance the ability of people to move fast and conveniently with the safety of all road users."

Now, when de Barros says, "economic" he means not only the literal, financial cost of road design, but especially the balance between the competing interests of users. This is where tough trade-offs get made. Think of designing a road like a balancing act. You have a bunch of different things you want to accomplish, but they are in conflict and competition with each other — and so compromises need to be made between form, function and cost.

But understanding how those competing interests get juggled, how those trade-offs get made, and how engineers' views are evolving can help us better understand how our roads work — and how they're going to change in the future.

Calgary's roads were designed in Ottawa

Get this: Important parts of Calgary's road design are actually made in Ottawa. How does that work?

Local decisions still get made around what kind of road to build — higher speeds and less access, or a slower local road with mixed use — and other design aspects like tree alignment. But there are federal standards that are a powerful force in shaping what our roads look like, how they work, and who they serve.

When streets get designed, traffic engineers don't just randomly decide to put a crosswalk here, a curb extension there, and, ooh, maybe some flashing lights over here.

Instead, they're following the national standards about such things, published by the Transportation Association of Canada (TAC).

Calgary's roads are often built based on design guides from the Transportation Association of Canada. (Scott Dippel/CBC)

The TAC did not respond to inquiries about its methods and requests for an interview. But both Alex de Barros at the U of C and Tony Churchill, the city's lead engineer for traffic safety, say the regularly updated standards of the Ottawa-based organization provide fundamental guidelines around traffic engineering that get implemented at the local level.

Engineers check the TAC guidelines when asking themselves things like: Where should we put a crosswalk? What style should it be? What about a flashing pedestrian signal? Is this too close to the next crosswalk? And what about the speed limit?

A familiar example is the crosswalk.

The Calgary crosswalk

Most marked crosswalks in Calgary are two simple, painted, parallel stripes across the road. This is the default "treatment" for a crosswalk.

Then there's the ladder-style crosswalk, which is a combination of the zebra-stripe style that's common internationally and our two-line crosswalk.

The ladder-style crosswalk is much easier for drivers to see from a distance, and thus arguably safer for pedestrians.

An example of the zebra-stripe pattern you see on some crosswalks. (Eugene Hoshiko/The Associated Press)

But the two-line crosswalk is still the default in Calgary, because that's what the TAC standards say it should be.

Churchill says the city is being more proactive in putting ladder crosswalks in at higher-use crossings with flashing signals. But, and here's an example of the balancing act, he argues that using the easily seen crosswalk style more often diminishes their effectiveness.

"If every crosswalk had a ladder crosswalk, those locations would be visible, but there wouldn't be any additional heightened awareness that that's a spot where you should be more aware of pedestrians than at other locations," says Churchill.

It's a weird catch-22: the ladder style is more effective, but engineers fear that overusing it will make it less effective.

If you like that quirk, here's another paradox: though intended for pedestrians, crosswalks have long been designed around the needs of cars, a sort of minor concession to those on foot. That perspective, however, is changing.

"Before it was, 'What's the traffic volume and how many pedestrians are there?'" says Churchill. "And now it's looking more at 'What is the actual cross-section [of roadway] that pedestrians are expected to cross? How is that operating in terms of speed and traffic volume?'"

Sometimes a crossing has enough traffic to warrant a higher-level treatment like a ladder crosswalk, or an overhead flashing signal, or the new flashing-LED side posts that the city has been conducting trials of — all in the name of safety.

An example of a rectangular rapid-flashing beacon (RRFB) crosswalk signal. (Richard Drdul/Flickr)

Those driver-pedestrian road features need to be balanced, but so does the cost.

Churchill says local engineers don't directly consider the expense of something in their decision-making — rather, they look at factors like traffic volume to make judgments about whether a higher level of treatment is justified.

De Barros argues that engineers are not immune to thoughts of dollar signs.

"We don't explicitly take cost into consideration, but implicitly, we do. If we think something is way more expensive than another solution, we tend to go with the cheaper one, unless we can justify the cost."

In other words, everyone can dream of building a road that is so magnificent it works for everyone, but the cost would be off the charts. That's fiscal balance.

But while infrastructure costs money, something like how fast people are allowed to drive involves the other kind of economic equation: the economy of competing interests.

Design a road, then set the speed limit

Consider the humble speed limit.

What is a speed limit, anyway?

Well, it's the legal maximum speed you're allowed to drive on a given stretch of road. But where does that limit come from? How do they determine what the safest speed is?

"Traditionally, that's been something tied quite closely to the function of the roadway," says Churchill. "Is this roadway meant to move traffic, or is it meant to provide access to adjacent land uses?" 

A speed limit sign indicates a maximum of 60 km/h along this stretch of Bowness Road N.W. in Calgary. (Robson Fletcher/CBC)

Think of Deerfoot Trail vs. Memorial Drive. One is to get you mainly through town, the other gives access to all sorts of side roads, communities and shops.

The way traffic engineers have traditionally set speed limits for decades, says Churchill, is by figuring out the "85th percentile" — that is, the speed that 85 per cent of people would naturally drive at or below on a particular road, given the width, number of lanes, frequency of intersections, and so on.

That speed then becomes the limit.

In other words, the road gets designed, and then the limit gets calculated.

"In North America, in general, the system we're operating under is still looking at how we expect traffic to behave and then posting the speed limit accordingly, as opposed to saying, 'This is the speed we want, how do we design our road to achieve that speed?'" says Churchill.

Couple that with de Barros' assertion that today's standards still favour cars over other road users, and you end up with a road system that privileges the convenience of drivers over the safety of pedestrians and cyclists.

"Most of the engineering standards for roadway design, and especially for those places where we expect pedestrians to [intersect], most of the studies have been done from the drivers' point of view," says de Barros.

But this is changing.

A different perspective

The TAC will publish new guidelines soon, and there may well be changes in design standards that focus on road safety, such as the use of flashing-LED pedestrian signals.

But both de Barros and Churchill say what's needed is wholesale change in our approach to road design.

They say the traditional approach has been to design roads around the needs of drivers, and then add on safety measures like crosswalks and signals after the fact. But building roads from the ground up with the safety of all users as a fundamental priority will be far more effective.

"It's not that historically we didn't value safety; it's just that we were relying on individual users to be perfect operators, which isn't realistic," says Churchill.

Tony Churchill, head of Calgary traffic safety, speaks with CBC Radio in this file photo. (CBC)

"I think that's the transition: actually designing for humans, as opposed to designing for people who will always obey the rules and be attentive," he says.

"If we really want to change how people are operating, then we have to change the road environment to signal subconsciously to drivers that this is the expected behaviour in that location."

For example, he says, we have to make the speed limit "credible" for the road by designing narrower roads where we want lower speed limits.

De Barros believes we still have a long way to go toward thinking of roads as genuinely shared spaces.

"The mindset until 20, 30 years ago was: You design roads for cars, period."

Engineering dogma has been shifting, but "that trend, however, has still not led to something that we could call an equal treatment [of all users]," says de Barros.

"We're not quite there yet. There's still work to be done there."

Calgary: The Road Ahead is CBC Calgary's special focus on our city as it passes through the crucible of the downturn: the challenges we face, and the possible solutions as we explore what kind of Calgary we want to create. This story is part of a sub-series on roads and how they shape our lives. Have an idea for a future story? Email us:

More from the Roads sub-series:

Other stories from the series:


Taylor Lambert


Taylor Lambert is a freelance journalist and author. He lives in Calgary and also on Twitter at @ts_lambert.


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