I've been looking at intersection design a lot lately between Collector Streets and Local Streets. Local streets should prioritise low speed and safety so why don't we adopt designs that support these priorities?
In BC/Canada at least, there are a few guidance documents that explicitly recommend such designs.
The BC Road Safety Toolkit is freely available and recommends them, it states...
"How it Works: In order to help draw drivers’ attention to pedestrian traffic and help make the right-of-way clear, raised crossings use the same materials as the sidewalk and bikeway, instead of those used for the road. Their purpose is to slow motor vehicles, improve the visibility of vulnerable road users, and encourage more drivers to yield to people crossing on foot or by bicycle. An added benefit of this safety design is greater ease of crossing for people with mobility or balance challenges (including people using walkers, wheelchairs, mobility scooters, etc.), because they do not need to step down from the curb.
Studies have shown that: Raised crossings can reduce vehicle-pedestrian crashes resulting in injury by as much as 46% and reduce vehicle-bicycle crashes resulting in injury by as much as 51%"
The TAC Traffic Calming Guide also recommends such designs. However, traffic calming is typically used to solve a problem with traffic volumes or speeds. But really traffic calming such as this should be an integral part of local road design, not an afterthought when speeding is later observed to be a problem.
When you look at the positives and negatives, you have to ask, 1) why we don't have more of these intersections, and 2) why anybody is designing anything else for Local Roads. Lets look at those positives and negatives...
I haven't included drainage or snow clearing in that list. There may be issues with drainage particularly if looking at a low cost retrofitted raised intersection, but if completely reconstructing the intersection or if its new construction, there is no reason why suitable catch basins can't be located appropriately to handle drainage where necessary. The raised intersection also may not allow a snow plow to pass through the intersection as easily, but that's not to say there aren't other ways to clear snow from such a design. As mentioned above, do we design for the infrequent event, or safety 24/7?
Did I miss anything? Let me know.