Ottawa city council seems on course to take what might seem like a bold step at its meeting Wednesday by approving the first-ever 30 km/h speed limit for some Ottawa streets.

Too bad it won't work.

There are a number of issues with the proposed go-slow policy. For one thing, there are so many caveats to qualify for the new, lower limit that relatively few corners of the city will ever meet them.

Here's a look at a few of the other speed bumps along the way to slower traffic.

Lowering limit has 'minimal impact'

Even in places that would qualify for the new speed limit, a posted 30 km/h sign alone won't slow traffic, and city staff know it.

According to their report on the policy, "studies have shown that reducing the speed limit on a roadway has minimal impact on the operating speed unless the roadway conditions cater to the lower speed limit as well."

"People drive at the speed they feel comfortable at, not what the posted speed is," said Heidi Cousineau, the city's program manager for area traffic management.

So what does slow vehicles down? Physical impediments, narrowing of streets and photo radar. It's the fear of crashing, damaging our cars, or hefty fines that lifts our foot off the pedal, not signage.

Bumps, bulges, staggered parking

The city uses different strategies for different streets. In some cases, speed bumps, humps or "tables" — basically a wider speed bump with a flattened top — are installed on side streets where speeding is a proven issue.

And because wide-open roads encourage speeding, the city's traffic management folks try to make streets skinnier to slow traffic.

This can be accomplished with physical stuff — curbs that bulge out in mid-block or at the corners, planters and raised intersections. In fact the city's own consultants suggest adding such physical features to streets that get a 30 km/h limit, just to make sure.

The city's own report says lowering the posted speed limit does little to slow traffic. (CBC)

Other measures such as painted bike lanes and on-street parking can narrow roads, too. Even making a crosswalk more visible — think of the rainbow-striped ones in Centretown — can have an impact on speed.

One of the more interesting techniques to calm traffic is staggered parking, where cars are allowed to park on just one side of the road, but the side where parking is allowed changes from block to block. The strategy works well on a relatively long street where parking is in demand.

"Staggered parking is not a physical thing, but it makes drivers feel more constricted," said Cousineau. "You can't just go straight down the road."

These measures slow average speeds down anywhere from 2 to 8 km/h, said Cousineau. If that seems minor, consider that a decrease in speed by even a few km/h means a driver can stop four or five metres sooner, depending on how fast the car is going in the first place.

That four or five metres can be the difference between a pedestrian being killed or seriously injured, and escaping tragedy.

Long wait list, expensive fixes

Councillors say speeding is one of the biggest complaints from their constituents.

Communities wait years to have their traffic issued dealt with. At any given time city staff have 60 small traffic measure requests on the waiting list, but the city only gets to five to eight every year.

And there are a dozen larger neighbourhood projects waiting; city staff complete about two a year. If a complaint involving a clear and present danger comes along, it goes to the top of the list, bumping other projects.

The fixes aren't cheap.

In 2012, council pumped $2.5 million into the traffic-calming program to clear out a backlog of projects left over from pre-amalgamation. But most years the budget is about $650,000.

A sidewalk bulge like this one can slow traffic by a few km/h, but can cost up to $50,000 to design and install. (City of Ottawa)

Speed bumps or tables added to existing roads can cost anywhere from $8,000 to $10,000 each. Narrowing a street by extending a curb or corner can come with a $50,000 price tag. A raised intersection goes for a cool $150,000.

Major traffic-calming infrastructure is almost never built as a retrofit.

"The bang for the buck isn't worth it," said Cousineau.

Instead, those sorts of measures are incorporated at an incremental cost into larger projects, such as the raised intersection at Queen and Bank streets, which was installed as part of the Confederation Line project.

Photo radar — cheaper option?

Last year city council asked the province to allow it to conduct photo radar pilot projects in school zones and on residential streets. But the Liberals are going one better: they're going to allow all municipalities to install photo radar in school zones and neighbourhoods that a city council designates as "community safety zones."

The proposed legislation envisions these special zones as ones that include a school, daycare, playground or park, hospital or seniors residence. The community safety zone designation can also be used for "collision prone areas."

Virtually any residential area would meet these prerequisites.

And so, instead of waiting years for a speed bumps, a community could apply for speed limits enforced by photo radar, which would actually make money as opposed to costing millions. In fact council has pledged to direct photo radar revenue solely to fund road safety measures.

A speed hump or 'table' is a speed bump with a flattened top, and costs between $8,000 and $10,000. (City of Ottawa)

As for effectiveness, consider the example of Medicine Hat, Alta. In a report released last year that reviewed a decade of photo radar data in the small city, officials found that average speed a 50 km/h zone monitored by photo radar was 48.7 km/h; for a 30 km/h zone, the average was 28.5 km/h.

It's hard not to see photo radar as the most cost-effective way to control speeding.

Sure, voting in a 30 km/h speed limit sends the right message. But it's an empty gesture if there's no enforcement to back it up.