The Province

Diamond intersecti­on weaves into Calgary

- TRISTIN HOPPER thopper@nationalpo­st.com twitter.com/TristinHop­per

In a Canadian first, the City of Calgary this week has partly opened a diverging diamond intersecti­on that eliminates the need to turn left against oncoming traffic.

The $78-million project is expected to dramatical­ly reduce congestion and crashes. At the moment of its inaugurati­on Monday, Calgary Mayor Naheed Nenshi even seemed to get poetic.

“Symbolical­ly, a bridge, bringing together two different sides, is a great way for us to continue to build community,” he said, adding that local commuters would no longer be “stolen away from their families” while waiting in traffic.

And, since it’s Calgary, at the ribbon-cutting workers at the diverging diamond intersecti­on were all presented with commemorat­ive belt buckles inaugurati­ng them as the builders of “Canada’s first DDI.”

Where Calgarians once had to turn left through a massive four-way intersecti­on, they will now follow a path that weaves them onto the other side of the road.

Anyone turning left, therefore, doesn’t face any traffic coming from the opposite direction. Drivers making a right, meanwhile, are peeled off before the weave.

The only signals at the intersecti­on are two sets of lights at the weave points.

The design is effectivel­y a slimmed-down version of the cloverleaf interchang­e, the famously convoluted arrangemen­t in which left turns are accomplish­ed by having cars drive on vast circles of roadway.

A cloverleaf requires no lights, but it also takes up village-sized plots of land. Had a cloverleaf been constructe­d at the site of Calgary’s new diverging diamond, it would have required the demolition of three or four nearby shopping centres.

As highway infrastruc­ture goes, the diverging diamond intersecti­on is surprising­ly young. U.S. traffic engineer Gilbert Chlewicki styles himself as the father of the DDI, saying he devised the concept in a 2000 term paper — although small-scale examples existed in Europe.

The first diverging diamond freeway intersecti­on opened in Springfiel­d, Mo., in 2009, and soon eliminated mile-long queues that had haunted the previous intersecti­on. More than 60 U.S. intersecti­ons since followed suit.

There were initial fears that asking motorists to briefly drive on the other side of the road would lead to devastatin­g crashes, but, safety analyses of the new crop of diverging diamonds have revealed the opposite. A 2016 study found that, on average, crashes went down by 33 per cent. The rate of crashes that caused injuries fell by 40 per cent. Cities are also turning to the design because of cost. In certain cases, a diverging diamond allows a city to speed up traffic with little more than fresh paint and new dividers: No major new overpasses need to be constructe­d. However, in Calgary, because engineers were working with a standard fourway intersecti­on, they needed to build a new elevated roadway.

Pedestrian­s and cyclists are funnelled through a protected path running through the centre of the intersecti­on.

Already, other Canadian examples of the diverging diamond are in the works. An intersecti­on is expected to open in Regina in 2019.

 ?? — THE CITY OF CALGARY ?? This week, the City of Calgary partly opened its diverging diamond intersecti­on, seen in an artist’s rendering, which is intended to reduce congestion and crashes. The $78-million project is the first of its kind in Canada.
— THE CITY OF CALGARY This week, the City of Calgary partly opened its diverging diamond intersecti­on, seen in an artist’s rendering, which is intended to reduce congestion and crashes. The $78-million project is the first of its kind in Canada.

Newspapers in English

Newspapers from Canada