Retrofitting Raised Intersections

With us staying mostly indoors these days other than a bike ride or walk round the neighbourhood, I figured I'd learn something I've always wanted to. Modelling transportation ideas in 3D. I signed into Sketchup Free and watched a few YouTube videos, and by the end of the day was reasonably competent building some basic 3D models of street features. My favourite topic of the moment is raised intersections as this simple improvement would significantly change how we view priorities at conflict points. Read on...

I've been through this a few times on this blog, first discussing the benefits and then later talking about how they have become part of Nanaimo's design guidance in both their engineering standards and Complete Street Design Guide currently being finalized. But we'll go through it again, this time with a focus on how we can retrofit raised intersection into likely most local streets. First the conventional intersection...

A conventional curb return intersection:

• Conveys priority for motor vehicles even though they do not have it.
• Requires curb ramps that are potentially awkward for people with mobility devices.
• Allows higher speeds of turning traffic entering and leaving the local street.

If we're going to retrofit a raised intersection, we have to remove the existing section of sidewalk, some curb and gutter and existing asphalt road surface as shown below in red.

We can then install the raised intersection in the same place, shown here relative to the existing curb radii in blue.

Of course, those radii we can still see above would be gone replaced with uninterrupted continuous sidewalk, and it would no longer appear like a conventional intersection. We now have a much tighter entryway for vehicles providing several benefits:

• The design conveys priority of pedestrians over motor vehicles.
• The design is more accessible for people using mobility devices.
• The design slows traffic entering and leaving the local street.

These could be implemented relatively easily at every local road intersection everywhere, and would help in prioritizing our streets to reflect most mode hierarchies. i.e., pedestrians first!