The interchange style selected for the Pilot Butte Access intersection – a “diverging diamond” – has never been built in Canada (more specifically, in Saskatchewan) where adverse winter driving conditions exist. The interchange will require drivers to merge into what is typically the oncoming lane as they cross over the main arterial roadway (in this case, Highway 1.)

Diverging Diamond

Image Credit:


The video below simulates an interchange similar to the one that will be built at the Pilot Butte access intersection.


Video Credit: Missouri Department of Transportation


A government-commissioned study of various interchange options for this access states the pros and cons of the diverging diamond interchange:


  • Fewer conflict points (enhanced safety)
  • Better sight distance at turns
  • Wrong way entry to ramps difficult
  • Ease of left and right turn movements
  • Increased capacity
  • Better vehicle storage between ramp terminals
  • Shorter signal cycle times required
  • Can synchronize signals at ramp terminals to minimize delays
  • U-turns can be easily accommodated
  • Typically requires less right-of-way
  • Construction time reduced


  • Driver unfamiliarity, particularly with merging on the left side and reversed flow
  • No standards currently exist, requires more design time
  • Additional signing, lighting and pavement markings required
  • No direct re-entry for traffic exiting the main highway (doesn’t support the bypass of over-height loads for a bridge that is too low)
  • No experience in the Canadian context


Exerpt from p.15 of the study:

Never Proven ScreenshotDownload the full study

The study also indicates that painted traffic lines are integral to the safety(8) of the design. This is likely because traffic using the interchange will need to cross over onto the left side of the road. The study also indicates that Saskatchewan winters may pose a challenge because road lines must be kept visible, despite seasonal snowfall. The study fails to indicate how the government, or their hired contractors, will overcome that challenge. Therefore, the increased safety advertised by government may be in question for the diverging diamond design.