How ‘green waves’ can make city riding better

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As you ride along Albert Street in Melbourne’s inner east there’s no indication of anything remarkable or out of the ordinary. It feels like the same inner-city street it was before; one of the most cyclist-friendly access points for those from the east.

But behind the scenes, there’s been a meaningful change to the way traffic flows on Albert Street; a change that will hopefully make cycling safer and more efficient along that route.

In April 2018, VicRoads — the local roads authority — changed the traffic light sequence along Albert Street as the first stage in a “green wave” introduced to serve the many cyclists that frequent the route. It’s a first for Melbourne, a first for Australia, and hopefully the first of many around the country.

Green wave?

At its most basic, a green wave is a series of traffic light sequences coordinated to give road users a smooth passage along a stretch of road. By travelling at a certain speed, users can “ride” the wave of green lights, moving along without being stopped at each intersection.

It’s not a concept that’s specific to cycling but in recent years green waves have been put to good use in aiding the movement of bike traffic.

David Taylor is an Industry Fellow at Melbourne’s RMIT University and one of the driving forces behind the Albert Street project. As he explains, green waves for cyclists have been used for many years in several cities around the world, including Copenhagen, Amsterdam and San Francisco.

“What was interesting about the San Francisco situation was that they were saying beforehand they had about a 20% noncompliance with traffic lights,” Taylor told CyclingTips. “Cyclists would go up to the traffic light, [see] there’s no traffic around, they can see what’s going on, and they go through a red light. Once they introduce the green wave they went to 100% compliance.

“Nobody went through a red light because you’re sitting in a green wave — there’s no point.”

Green waves have been used to great effect elsewhere in the U.S. too.

“When they did this in New York they found that by implementing a green wave for bikes, it sped up the cars,” Taylor said. “And the theory that they had was that the interaction between the cars and the bikes was more predictable. And when the interaction was more predictable you didn’t get this start-stop-start.”

Why is the interaction more predictable? Given that riders are incentivised to ride at a certain speed, they end up riding together in a group, all at a similar speed. This makes riders more visible, and safer.

“If you look at it today you’ve got people that are racing along trying to get the green light, they’re going flat-out,” Taylor said. “Then you’ve got people that are just dawdling along and they’re spread all over the road because there’s no coordination of them. If you put them into a green wave you start ending up with something very visible to cars.”


Green LEDs in action on a Copenhagen green wave.

For the past few years Taylor and his team at RMIT have been collaborating with the City of Melbourne and VicRoads to introduce green waves to Melbourne. While implementing green waves is already tricky — requiring the coordination of multiple intersections’ traffic lights, sign-off from multiple authorities, the need to balance the requirements of all transport modes etc. — the presence of trams makes things particularly challenging in Melbourne. Which is why Albert Street is a logical place to start.

“Albert Street’s probably ideally suited because there’s minimal tram crossing,” said Ross Goddard from the City of Melbourne’s Traffic Engineering team. “Also bicycles, and in some regards traffic as well, are generally travelling in peak directions. So the majority of cyclists are coming into the city in the AM and out of the city in the PM. A lot of the cross streets are local roads so it’s probably a great street for us to start with and see if we can get a good result.”

Albert Street

Taylor worked with a team of RMIT undergraduate students to create models of what an Albert Street green wave might look like. They played around with various rider speeds by looking into average rider power and traffic light timings, all while monitoring the impact on traffic flow for riders and for drivers. After more than a year of work, RMIT and the City of Melbourne presented their proposed traffic light sequences to VicRoads who implemented the changes in April 2018.

There was no announcement about the green wave’s implementation and when you ride or drive along Albert Street, there’s no way of telling it’s in place — as yet there are no signs or green LEDs on the roadside like in the Copenhagen example (see video above). But on the 1.1km stretch of Albert Street between Lansdowne Street and Hoddle Street, traffic signals have been changed inbound during the morning peak (from 7-9:30am) and outbound during the evening peak (3:30-6:30pm) to suit cyclists.

The speed you’ll need to ride at in order to stay in the green wave depends on whether you’re heading inbound (west) or outbound (east) and which section of Albert Street you’re on. (The Albert Street green wave is believed to be the first in the world with different speed limits along its length, owing to the need to account for a not-insignificant hill between Powlett Street and Clarendon Street):

Outbound:

– Landsdowne Street to Powlett Street (mostly downhill): 22km/h
– Powlett Street to Hoddle Street (flat): 26km/h

Inbound:

– Hoddle Street to Simpson Street (largely flat): 22km/h
– Simpson Street to Powlett Street (slightly uphill): 26km/h
– Powlett Street to Clarendon Street (uphill): 17km/h
– Clarendon Street to Eades Street (flat): 24km/h
– Eades Street to Lansdowne Street (slightly uphill): 20km/h

The Green Waves on Albert Street are about 40-45 seconds long. This means that if you start behind the front of the wave, you can travel faster than the indicated speeds while still being within the wave. Similarly, if you start at the front of the wave, you can travel slower than the indicated speed and still make it through the wave.

A map of Melbourne’s Albert Street green wave, showing the elevation of the street and the speeds required to stay in each section of the wave.

Analysing Albert Street

Looking at these speeds there’s one figure that stands out immediately: the 22km/h on the 700m descent from Lansdowne Street to Powlett Street. While not hugely steep, this is a fast section of road and it’s easy to get to well beyond 30km/h without pedalling. Slowing down to 22km/h will take a concerted braking effort from most riders — one which might not seem worth the hassle.

Goddard and Taylor are aware of how slow 22km/h will feel along that section, but the low speed is by design. They want cyclists to slow down, in order to increase safety.

While there’s a protected bike lane on that descent, its safety is compromised by several driveways on the left-hand side, particularly into the Tribeca Serviced Apartments. Drivers turning across the bike lane pose a real risk to rider safety and the hope is that by slowing down traffic, safety can be increased.

“We’d like to hope that the green wave, as well as meaning that cyclists get less delays along the whole length, could also make them more happy to travel at a reasonable speed down that path because there would be no need to rush to get the light,” said Goddard. “And the in-ground [green LED] lights, if we did go down that path and could get the funding, would really help to say ‘Hey, no need to speed up here. You’re going to get ahead of the lights.’”

While experienced cyclists might be frustrated by the 22km/h speed, ultimately, the green wave isn’t targeted at that market — it’s designed for the average commuter cyclist and helping to make it safer and more appealing for such riders to get on their bike.

Valencia Street in San Francisco’s Mission District has a green wave, with a clear target speed.

So what impact has the green wave had? Initial data suggest that the ride inbound is now an average of 53 seconds faster during the AM peak. The ride outbound is, on average, three seconds faster — not a meaningful improvement but that’s due to a couple of factors. For a start, traffic lights at Hoddle St (the outer edge of the green wave) operate on a 160-second cycle, twice that of Landsdowne St (the inner edge of the green wave). This means that, even if you’re heading outbound in the green wave, you’ll still get stuck at Hoddle Street half the time.

Secondly, outbound ride times haven’t improved considerably because the green wave has had the effect of slowing traffic on the Albert St descent. Where the average descending speed was around 33km/h before the green wave’s introduction, it’s now around 28km/h.

As for drivers, travel times have increased marginally along Albert Street in a consistent manner since 2010, as further bike infrastructure has been installed. The addition of a green wave has had what Goddard calls a “minimal impact”. In the evening peak, for example, there was already a queue from Hoddle Street back to Powlett Street before the green wave was introduced. As Goddard explains, instead of cars going 50km/h to join the back of the queue, they now go 22km/h before having to stop.

The road ahead

The next step for the Albert Street green wave is to install LEDs in the roadside. These green lights would do more than show cyclists that they’re set to get green lights — they should also improve rider visibility and safety.

“As people start seeing these green lights in the road, they will realise that could be a cyclist wave about to come through,” Taylor said. “So if you’re driving your car and you go to turn right into a parking structure near Melbourne Central or something like that and you see green LEDs on the road it could be like ‘Ooh, hang on a minute – there could be a bike.’”

There’s another benefit to having LEDs in the roadway, too.

“Really what we want to do is have some sensors in the LEDs so they could either be Bluetooth sniffers, Wi-Fi sniffers or just simply infrared scanners that as people go past we’re measuring the frequency of people going through,” Taylor said. “Ideally we want the system to be self-regulating.

“With cars you don’t need to worry about hills, unless it’s a steep hill, and you don’t need to worry about wind — they’re just going to go at the speed limit. Whereas [with] bikes that’s not the case. If it’s a strong wind or a large hill the speed difference is really dramatic and so that’s where those sensors could come in … It could be that the speed is actually two k’s slower on a particular day because it’s a roaring headwind as opposed to a howling tailwind.”

The initial plan had been to have green LEDs installed by the start of 2019, but RMIT, the City of Melbourne and VicRoads ran into supplier issues that scuppered those plans. The plan is still to install the LEDs at some point, but a revised date has not been set.

Beyond Albert St

So what about beyond Albert Street? Could we see more green waves introduced in Melbourne in the years to come? As Goddard explains, it gets tricky when you start looking at the Hoddle Grid of Melbourne’s CBD, even on the relatively cyclist-friendly La Trobe Street.

“My initial discussions with VicRoads suggest that [La Trobe Street’s] highly unlikely because of the competing demands of trams going both ways, bikes going both ways, high pedestrian numbers and also just the linking to all the other intersections within the Hoddle Grid — they’re sort of all in sync,” Goddard said. “I think that one will be difficult but there might be other opportunities in other streets outside of the CBD.”

One target could be Canning Street in Carlton, a key cycling thoroughfare for those coming from the north. There are tentative plans to start investigating Southbank Boulevard as well. And there’s also talk of better linking Albert St with Wellington St — a key cycling corridor for those heading north out of the city.

For now though, Albert Street remains the only green wave in Melbourne and indeed in Australia. Hopefully other such projects will spring up in its wake.

In the grand scheme of things, changing the traffic light sequences on one strip of road might seem like a minor development, but this is a promising step forward. As our cities continue to expand, traffic builds on our roads and public transit comes under increasing strain. To help combat this, governments are starting to spend more time and energy on cycling for transport.

Green waves are a low-cost way for those governments to help achieve these aims, by providing a safer and more efficient way for cyclists to move through our cities. And that’s a good thing for everyone.

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