Green Waves for bicycles in Copenhagen
“The ‘green wave' for cyclists was one of the greatest ideas to come out of the brainstorm started by former actor Klaus Bondam when he was elected on to the city council.”  He was leader of the Technical and Environmental Administration, the unit responsible for Copenhagen's traffic policy.
Before 2004, traffic lights were coordinated in favour of cars, but the idea was to adjust them to make cycling easier and quicker. “On most major arteries leading into the city centre, the traffic lights are coordinated to allow continuous flow of traffic, allowing cyclists to flow into the city in the morning rush hour ... The lights reverse in the afternoon to send people home on a simple, tech-based tailwind.”  The principle is simple: “at a speed of 20 km/h, cyclists during rush hour can surf a wave of green lights through the city without putting a foot down.” 
Green waves for cyclists were established in three streets: Nørrebrogade (the location for a pilot from 2004), Østerbrogade and Farimagsgade. A string of green lights embedded in the bike path — the ‘Green Wave' — flashes on, helping cyclists avoid red traffic lights. It was decided on, and implemented by, the city's Department of Traffic.
That was Green Wave V1.0. “The City [of Copenhagen] is currently testing a pilot project involving a detection system on Østerbrogade. Green Wave 2.0. It will detect bicycle users approaching an intersection. If there are five or more cycling citizens roughly cycling together, the light will stay green up ahead until they pass.” 
Copenhagen is famous for its bicycle-friendly highways, with broad two-lane cycleways clearly separated from the road. “Today, 36% of the population travel to work or school by bicycle [and] 1.1 million kilometres are ridden on bicycle in Copenhagen every day.” 
However, cycling was still a stop-start process, with traffic lights favouring cars and buses and bicycles unable to maintain an even speed. In order to cut the use of fossil fuels and ease mobility, and help the city meet its goal of becoming the world's first carbon-neutral capital by 2025, there was still more to be done to support cyclists, in particular to make their journeys quicker and safer.
The public impact
The evaluation report on green waves on Nørrebrogade, the road where Green Wave V1.0 was established, showed that “travel time decreased by 17 percent for a cyclist who cycled out of town at 20 kilometres per hour”.  Moreover, the number of stops fell from six to under one. In the opposite direction, the number of cyclists' stops decreased by the same percentage, with a slight decrease in travel time.
Transport by bus was initially adversely affected. Evaluations of Green Wave V1.0 showed that it had an unfortunate side-effect, increasing travel time for buses by up to 14 percent. “Adaptive systems are being used which prioritise between bikes and buses using data from traffic sensors and GPS in buses dynamically, in such a way that the buses are not delayed.” 
Considering that so many of Copenhagen's citizens (60 percent of voters and most children and teenagers) use bicycles as a means of transport, the objective of the programme were in line with the interests of the public.
However, there was a lack of involvement of other stakeholders, such as public transport bodies, in the formulation and implementation of the Green Wave. It was implemented by the Department for Traffic, without having to involve other departments, or residents or other actors before project implementation.
The Green Wave programme has the support of the municipality and its Department of Traffic and has been backed by municipal funds. In Copenhagen, there is usually support for pro-cycling policies, from both politicians and citizens. The idea was initiated by Klaus Bondam, who served on the city council from 2002 to 2010. He is now the director of the Danish Cyclists' Federation
The initiative has the normal characteristics of pro-cycling policies - promoting wellbeing through lower congestion and improvements to the environment, general health, and urban life. There are also more political motives:
- Such projects can often be implemented within a single term in office.
- Bicycle policies are relatively inexpensive and highly visible and popular with the many cyclists.
Public confidenceSince the majority in Copenhagen use bicycles and the policy received no objection from motorists, public confidence is relatively high. The mayor who proceeded with the policy, Ritt Bjerregaard, was from the Social Democrat party, which was re-elected in 2010.
Clarity of objectivesThe Green Wave initiative sits comfortably within Copenhagen’s overall environmental objectives of achieving Copenhagen's aim of becoming carbon-neutral by 2025. The specific objectives of the Green Wave are to improve cycle flow through the city, in particular keeping cycling speeds at a relatively constant level and minimising the number of stops cyclist need to make at red lights. These objectives have been maintained consistently during the Nørrebrogade pilot and the more extensive roll-out.
Strength of evidence
The programme was the first of its kind, so it had no precedent in cycling, although the principle of the green wave had been applied on urban highways, such as London's Marylebone Road.
There was a pilot phase, which was used as the basis on which the programme was finally adopted, the test phase on Nørrebrogade in 2004. The pilot was very successful, the average travelling speed of the cyclists increased and, in general, cyclists did not need to stop.
There were a number of technical feasibility considerations:
- To measure the travelling speed of the cyclists, a GPS- and GIS-based technology was developed which took into account factors such as the number of cyclists present in the lanes at the time of the measurement.
- The evaluations from the Green Wave V1.0 showed that using a static average speed to control the system wasted a lot of potential, as it did not take into account any variations in average travel speed that may result from variables such as weather (wind, rain, snow, etc.) or the amount of traffic on the cycle lanes. However, this problem has been addressed by Green Wave V2.0
- Detecting groups of cyclists and prioritising them at intersections were, and still are, being tested.
Financially, it was easy and cheap to implement because no new construction was necessary, although a certain amount of technical equipment was required.
Concerns regarding the effect of the Green Wave on bus and car traffic were evaluated, based on the results from the pilot. “As a consequence, minor adjustments for public buses were integrated into the system.” 
One challenge for the city was to communicate the speed the cyclists should ride at (20 kilometres per hour) to reach the next traffic light and ultimately the whole green wave.
ManagementThe Green Wave programme was introduced by the Copenhagen City council has part of their wider initiatives to constantly improve cycling in Copenhagen. Copenhagen ambitiously aims to become the worlds’ best cycling city by 2025.  The Traffic Department within the council is responsible for managing bicycle initiatives within the city, with extensive experience due to a long cycling history in the city.
The effect of the Green Wave is monitored and evaluated regularly, and the results are then incorporated in the formulation of the approach. However, the programme still lacks a central monitoring system.
There is evidence that there the results and obstacles faced after implementation of Green Wave V1.0 were monitored and taken into consideration in implementation of the next phase. Evaluation reports were used to measure the impact and effectiveness of the Green Wave.
In the action plan 2015-16, the city sets out a number of indicators, including: “From 2013 to 2015: percentage of all bike trips to work and places of education in Copenhagen to rise from 41% to 50%. Compared with 2010, cyclists' travel time to be reduced by 5% in 2015, 10% in 2020 and 15% by 2025”. 
The action plan also indicates what is being done to improve the Green Wave programme. "Today, green waves function in isolation without any coordination behind them. For this reason, work is being carried out to link them together. It must be possible for the green waves to be monitored and adjusted by means of a traffic management system based on measurements of the cyclists real travel time, number of stops.” 
In general, the main actors - the city council, particularly the Department of Traffic, and the cyclists themselves - are very strongly aligned. There have been some problems in reaching this alignment, for example:
- Cyclists rarely have an intuitive understanding of how fast they are going or any speedometer equipment to tell them. It was a challenge for the city of Copenhagen to find a manner of communicating the speed at which cyclists should ride for the Green Wave to work successfully.
- While Green Wave V1.0 had no adverse effect on cars' average speed, it did slow down buses. As a result of this, modifications were made (see Public impact above), to address the concerns of public transport bodies.
- Green waves have for a while been functioning in isolation without any coordination behind them. For this reason, work is being carried out to link them together.
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