A protected intersection is about more than just corner islands and two-stage left turns. A truly protected intersection is safer for all modes… Essential elements include the dedicated left and right turn lanes on all vehicle approaches and signal phasing that combines to eliminate all conflicts… Let’s pick it apart a bit…

I’ve passed through this intersection in Utrecht so many times and for what is a pretty busy street with a lot going on I've always felt completely safe riding through it in a way that isn’t common in North America. It has a lot of the key elements that make Dutch intersections so much safer for everyone, whether they’re driving, walking, or riding a bike… It’s not easy to capture all of that in one photo, so the plan view is shown below along with some key design elements… The photo above is taken on the west leg looking east…

I think that pretty much every single high level planning document I've ever read says we’ll prioritize safety above all else, but few intersection designs in North America actually apply that to every facet of intersection design and operation. Furthermore, it’s not possible to achieve everything at every intersection, but let’s get into what’s so good, and where some elements might not be possible…

Step 1: Allocate space for all modes first

If we’re serious about mode shift, safety, and equity, to name a few reasons often cited for intersection upgrades, and if we prioritize those things over vehicle capacity, then we start to make different choices in our designs. The basic requirements for the perfect signalized intersection that works for everyone should be:

Sidewalk on each side
Bike path on each side (unless bi-directional on one side makes more sense)
Vehicle left turn lane
Vehicle through lane
Vehicle right turn lane
Vehicle receiving lane
Maybe bus lanes

If we have space for a bus lane or even more vehicle lanes like we have in the example above after the basic requirements have been met, then go ahead, but only after all other needs have been accommodated. That might be a hard sell when existing intersection designs create a pattern of traffic that we think we have to accommodate now and into the future, but we don’t always; if there are alternatives, be that alternative routes, alternative modes, or even alternative times to make a trip, people will adjust, traffic evaporation is a real phenomenon…

In terms of space, and considering general North American minimums, we need 1.8m for the sidewalk on each side, I'd say 2.1m for the bike path on each side, 3.3m for each of the four vehicle lanes, that’s around 21 metres already, then throw in the curb and gutter, whatever separation is added between modes, for boulevards, median islands, or on-street parking that may also be provided. A right-of-way of 25-30 metres should accommodate such an intersection comfortably.

Step 2: Adopt No Right Turn on Red on all approaches

No Right Turn on Red (NRTOR) is the default in the Netherlands and many other countries. It used to be the norm in North America too until an oil crisis in the 70’s sought ways to save gas and NRTOR was one of those ways… Interestingly, the Netherlands used that same crisis to build out their bike network and reduce their reliance on the car. North America chose another path… But we are where we are.

NRTOR is becoming more common today, and hopefully one day we see more cities, provinces, or even the country re-adopt it as a standard. Until such time, it’s as simple as adding the NRTOR sign to each approach. NRTOR provides four primary benefits:

It improves safety by reducing conflicts between cars.
It improves safety by reducing conflicts between cars and people walking or using a mobility device.
It improves accessibility for people using a mobility device as drivers should be stopped behind the stop bar and therefore not blocking the crosswalk and curb ramp.
It improves safety by reducing conflicts between cars and people riding bicycles.

There may be some compliance issues early on, but hopefully over time, people get used to it. If compliance issues persist, I’ve seen some LED versions of the NRTOR sign, and something that could work even better would simply be a set of red, yellow and green turn arrows… It would be much more intuitive… The only problem, in BC at least, is that the Motor Vehicle Act acknowledges both green and yellow arrows, but not red like we see in that Dutch example above…

Step 3: Plan Signal Operations for Safety

When we have the above elements in place, it allows the intersection to operate in a way that removes all conflicts. There are a few key principles for signal operation:

Through traffic goes with through pedestrians and bicycles.
Left and right turns are both protected.

Basic signal stages and phases are typically as follows, albeit the order may vary, and stages may be skipped if demand is not detected…

This method of operation removes all conflict if people drive with care and to the law. It’s still possible that drivers will jump a red light, ignore a NRTOR, or get distracted by their phone and rear-end someone. A reminder that safe system design is not about eliminating all collisions, but those that are severe or fatal.

Step 4: Add-ons

Steps 1 to 3 get you to a pretty good place, but there’s more that can be done:

Countdown to green timers let people know their turn is coming, this is most well used in the Netherlands for people riding bicycles, but could equally apply to people walking and driving. When you know your turn is coming, you’re more likely to obey the signals.
Turn calming by forcing a tighter radius can slow turning traffic and improve safety. This is less important with the perfect intersection as conflicts such as walk with traffic are removed, but slower turning traffic is never a bad thing and supports that safe system strategy of reducing the likelihood of a serious injury or fatality if someone does something they shouldn’t.
Add bicycle lean rails to make the wait for green on a bicycle a bit more comfortable.
Directional pedestrian and bike push buttons allow for efficiencies, if the signal knows a person is only crossing in one direction, they can shorten the intergreen with a conflicting traffic phase. If the signal knows there are only people biking and not walking, it can skip the long walk time.
Adopt near side signals that discourage drivers creeping over the stop bar, keeping crosswalks car-free and accessible.
Take care to keep curbs low or tapered to eliminate the chances of clipping a pedal.
Add Tactile Warning Surface Indicators (TWSIs) to guide anyone with sight loss walking through an intersection.

Step 5: If you can’t do all that…

If it’s not possible to provide separate right turn lanes, and separate turning traffic from crossing pedestrians and cyclists, start to think about these mitigations to reduce conflicts:

Leading pedestrian and bike intervals can give people walking or on bicycles a head start on traffic.
Provide additional signage to better alert drivers. The Dutch use the flashing ‘Let Op’ sign, ‘Pay Attention’ in English, while Vancouver has an example of RT Yield to Cyclists sign with flashing LED’s activated by approaching cyclists.
Bend-out bike paths and crosswalks to improve sight lines between turning drivers and people walking and cycling.