1. Two-lane roundabout with two-way bike path
Harderwijk, Hoofdweg/Verkeersweg, two-lane roundabout. On this two-lane roundabout with a two-way bicycle crossing too many accidents occurred. Local authorities have increased safety by a three-pronged approach: 1) construction of a raised crossing, 2) increasing the distance between crossing and roundabout and 3) adapting the arrow markers for motorists.
2. Location and traffic volume
The roundabout is located at the edge of the town centre, at an intersection of two through roads. Over 20,000 motor vehicles per 24 hours use the roundabout. For cyclists the route along Hoofdweg to the town centre is most important. In addition there is a two-way cycling route along the south of Verkeersweg that is heavily used, by school-age children in particular.
3. Construction two-lane roundabout
In 2000 traffic lights at this intersection were replaced by a roundabout. In order to ensure a speedy circulation for motor vehicles a decision was made in favour of a two-lane roundabout, constructed largely in accordance with the recommendations of CROW-publication 126: 2 lanes on the approaches,1 lane on the exits, circular bike path at 5 metres’ distances from the lanes and priority for cyclists. The south leg was provided with a two-way bicycle crossing.
4. Many accidents
From the very first year after construction numerous accidents occurred.. In 2002 and 2003 28 accidents occurred, 6 of which with injuries. On the one hand these were priority accidents* between cars and cyclists on the exits Hoofdweg and Verkeersweg-west. Often injuries were incurred, particularly among cyclists between 12 and 15 years of age. In addition there were many weaving and rear-end collisions among cars at various locations on the roundabout. In these accidents only material damage was incurred.
*) Actually these were passage accidents. Drivers leaving the roundabout failed to give free passage to cyclists continuing on the roundabout.
5. Causes of accidents
An analysis revealed many accidents to be the result of too high a workload for drivers. At this compact roundabout car speeds were relatively high. As a result drivers had to perform many actions and make many decisions in a very short time, particularly drivers on the inner lane who had to weave in order to leave the roundabout. This resulted too often in overlooking the cyclists on the exit. A major cause of the rear-end collisions was moreover the limited room in front of the bicycle crossing. This lead to rear-ends of vehicles sticking out over the roundabout when motorists had to wait.
6. Additional measures
A number of measures have been taken to increase safety: 1) the two-way crossing has been raised; 2) two bicycle crossings have been relocated at a greater distance from the roundabout; 3) signs and markings* for motor vehicles have been adapted. The measures resulted in a significant decrease in the number of accidents. In 2006 and 2007 only a single accident occurred on the connections. The following pictures provide the details of these measures.
*) The arrow markings have not been executed as planned, see chapter 9.
7. Two-way raised crossing
By raising the two-way bicycle crossing the visibility and conspicuity of the crossing are heightened. In addition the raised level has a calming effect on car traffic. The pedestrian crossing has been raised at the same location. In order to emphasise the right of way the bike path has been executed in red asphalt. Axial markings, in addition to signs, indicate this is a two-way bike path.
8. Distance to crossing
By increasing the distance between the roundabout and the bicycle crossing to approximately 10 metres, there is now more room for cars having to give free passage to cyclists. Consequently they no longer take up room on the roundabout itself. An additional advantage is that there is also more room for cars waiting at the entrance to the roundabout, so drivers having to yield to traffic on the roundabout cause less obstructions for cyclists. The extra distance was also desirable for the construction of the raised level, as it provided more room for fitting in the slopes. Motorists do not like waiting on a slope.
9. Marking and signs
In order to reduce the number of (sudden) weaving manoeuvres on the roundabout, markings and signs on the approaches have been adapted. Only left-turn traffic is referred to the inner lane and has to weave in order to leave the roundabout.
10. Discussion about alternative solutions
Removing the right of way of cyclists has been considered, but this was rejected on the grounds of uniformity and cycling quality. Discontinuing the two-way crossing has been considered as well, but this would be highly illogical for cyclists on the two-way bicycle route. Not many school-age children will meekly travel three-quarters of the way around the roundabout. A tunnel proved to be not feasible and too expensive. A turbo roundabout was rejected since this would require a two-lane exit. These exits are undesirable due to the danger of blocked-view accidents. Semi-turbo roundabouts that render weaving on the roundabout redundant as well and have moreover single-lane exits (zie Hilversum), did not yet exist at the time
- Alle hoofdstukken
- 1. Two-lane roundabout with two-way bike path
- 2. Location and traffic volume
- 3. Construction two-lane roundabout
- 4. Many accidents
- 5. Causes of accidents
- 6. Additional measures
- 7. Two-way raised crossing
- 8. Distance to crossing
- 9. Marking and signs
- 10. Discussion about alternative solutions