1. All Directions Green in Groningen
Groningen, Herebrug-Zuiderpark, all directions green. In order to make traffic lights more bicycle-friendly, local authorities in Groningen often use the solution of providing cyclists with a green light for all directions (ADG=All Directions Green) simultaneously. In over one-third of all ADG regimes the cyclist receives green twice a cycle, as well. This will be expanded in future. In this case the ADG regime at the intersection Herebrug-Zuiderpark is shown.
The intersection lies on the principal bicycle route (along Hereweg) from the southern suburbs to the town centre. Hereweg is also of major importance for car and bus traffic. Stationsweg and Zuiderpark, at right angles to Hereweg, are part of the central motor vehicle ringroad. Due to the presence of the train station a large number of buses use the intersection. Most cyclists towards the train station use another route, over Museum bridge.
3. Intersection flows
Approximately 17,000 motor vehicles and 9,000 cyclists use this intersection daily. The north-south direction is clearly dominant for cyclists (two-thirds of all cyclists). Approximately 20 per cent of cyclists makes a left turn. ADG has particular advantages for this group. The dominant direction for car traffic is east-west, which means at right angles to the dominant bicycle direction. Moreover a large number of cars turn from south to east and vice versa. Which means that the busy bicycle direction from the south to the town centre crosses four heavy flows of cars.
4. The regime
The intersection regime is traffic-actuated. All bicycle and pedestrian flows are settled in a single phase (ADG). Outside of peak hours cyclists have as a norm green twice per cycle, during peak hours only when the amount of traffic allows this. Interference by buses, too, is only possible outside peak hours. Maximum cycle time is 120 seconds (the aim is 90 seconds). This means that waiting times for cyclists in peak hours may often be very long, on average over 40 seconds. In comparison: the CROW Ontwerpwijzer Fietsverkeer recommends an average waiting time of less than 15 seconds. The regime is part of a small network regime (TopTrack( involving 3 traffic lights (see map in chapter 2). This intervenes when there is a large supply of motor vehicles on the east-west route.
The intersection is relatively compact. Three of the approaches have bike paths, the fourth has a bicycle lane with a separation of Gummatec bars. A physical separation between car and bike is advisable to prevent cyclists from responding to the lights meant for cars. In this way the conflict between cyclists and pedestrians is kept outside the regime, so they can easily be combined into a single phase. The bike path on Stationsweg is a relatively recent addition (2004). Before that time Stationsweg was mixed-traffic and cyclists from this direction did not participate in ADG. So until 2004 this was a regime of three directions green at the same time.
6. Lay-out (continued)
For motor vehicles two or three lanes are present on all approaches. There is therefore space to separately regulate car directions or buses. Priority has been decided in favour of the east-west flow. This is emphasised by red bicycle lanes with block marking and give-way markings running east-west over the intersection itself. No other markings occur on the intersection.
7. Right-turning cyclists
According to local authorities, cyclists are allowed to turn right when the light is red, but at the time of our visit to this intersection the relevant signs were absent (‘Probably taken by students for a souvenir’). In actual practice most right-turning cyclists jump the light anyway, even in the absence of signs. In addition, many right-turning cyclists from the south often ride on the pavement, as the bike path is jammed with large numbers of cyclists that want to ride straight on.
8. Advantages ADG
The two major advantages of ADG are: (1) there are no longer any partial conflicts between lorries and cars making a turn and cyclists riding straight on and (2) left-turning cyclists can cross the intersection diagonally. This is usually faster for these cyclists. In addition there is no need for positioning space to ensure cyclists may turn left in two stages. For cyclists riding straight ahead ADG is only faster when combined with twice green per cycle.
9. Chaotic scene
A drawback of ADG is that somewhat chaotic scenes occur when cyclists from all directions enter the intersection at the same time. This may be particularly awkward for less confident cyclists. Right of way is unclear as well. A green light means ‘go’ and overrules signs and regulations regarding right of way (but not the regulations concerning free passage). In actual practice cyclists often resolve this among themselves without any problems. Moreover, a collision with another bike is usually far less consequential than one with a car or lorry.
10. Missed opportunity
A second drawback of ADG is that not all green opportunities for cyclists can be used. Cyclists may only receive a green light when lights for all cars are red. Consequently it is impossible to have a particular bicycle direction benefit from time remaining in the regime. For instance pedestrians travelling south-north sometimes are awarded extra green when there is no traffic in the conflicting direction. The many cyclists in the same direction can not benefit as well, since left-turning cyclists, getting a green light as well, will come into conflict with cars from other directions. In addition experience has taught that all bicycle directions should really have green at the very same time. If a single bicycle direction receives a green light slightly ahead of the others, this will often entice cyclists in the other directions to start riding as well (green lure). These cyclists may come into conflict with nearby car directions that have not cleared yet. Starting the ADG phase is therefore delayed until the clearance time on the most critical bike direction is past.
11. Red light negation
The number of cyclists jumping the lights (with the exception of turning right) seems to be small. This despite the long waiting times during peak hours. It is clear to cyclists that they are not waiting in vain. The majority of the time there are crossing motor vehicles. In addition it is physically impossible for many cyclists to jump the light as other waiting cyclists obstruct their passage.
12. Traffic safety
Accident statistics are favourable. The majority of accidents with material damage only (ums) are between motor vehicles. The number of ums has fallen, possibly in part by the intersection adaptations in 2004. Over the past 5 years there have been 5 accidents with casualties, two of which had to be hospitalised: 1 in a collision between two cars and 1 in a collision between two bikes. Although the low number of accidents with casualties does not allow definite conclusions, it is remarkable that there are no serious accidents between cars and lorries on the one hand and cyclists on the other. This appears to be really thanks to ADG.
Daniël de Haan, Theo Zeegers en Piet van der Linden , Verkeerskunde
Praktijkvoorbeelden laten zien dat veel kan worden gedaan om het oponthoud voor fietsers bij verkeerslichten te verminderen, zonder de doorstroming van het autoverkeer aan te tasten.
Theo Zeegers , Ketting
Alle Fietsers Tegelijk Groen bij een kruispunt met VRI: De Fietsersbond zet de voordelen, nadelen en randvoorwaarden op een rij.
Notitie van het Fietsberaad over de verkeerskundige en juridische aspecten van 'alle fietsers tegelijk groen' bij verkeerslichten.
Suzanne van Lieshout (NHTV) , Fietsersbond enfb
Evaluatie van een aantal verkeerslichtenregelingen met vier richtingen groen.