Objective and subjective road safety of the Rhenen-Achterberg intersection on the N233 provincial road : Inventory of concerns among residents, survey among (parents of) students and assessment of the current and future traffic situation. The province of Utrecht asked SWOV to investigate the objective and subjective traffic safety at the intersection of the Bergweg/Achterbergsestraatweg and provincial road N233. It is an intersection between a 80 km/h rural distributor road under the authority of the province of Utrecht and a 50 km/h urban distributor respectively 60 km/h semi-urban access road under the authority of the municipality of Rhenen. Along the N233 there are separate (one-way) cycle paths. The intersection is signal controlled and has separate at-grade bicycle and pedestrian crossing facilities. Parallel to the N233 is a railway line. The railway crossing is at grade but fully guarded. The intersection is relatively busy. In the near future the province of Utrecht wants to redesign and upgrade the N233. In the new situation extra through lanes on the N233 will be provided to increase capacity at the intersection and extra lanes will be constructed on the Achterbergsestraatweg-East. The N233 will also be provided with a physical median in the form of a centre island. On the west side a bicycle link will also be constructed between Achterbergsestraatweg-West and the cycle path along the southern part of the N233. The bicycle and pedestrian crossings remain at-grade crossings. New traffic signals and adapted signal plans will be implemented. The new timing plans provide for a dedicated (conflict-free) signal phase for cyclists (green light for all cyclists while all other traffic has a red signal). In this way conflicts cannot occur if all road users abide by the rules. The residents action group WWVO (abbreviation of ‘We Want to Cross Safely’ in Dutch) considers the intersection dangerous and does not agree that the proposed new design of the Province will resolve the problems. The residents action group is concerned about cyclists (mainly students) who need to cross the intersection. WWVO has prepared an alternative design for the intersection which incorporates a grade separated crossing for traffic crossing from East to West and vice versa. The study addresses the following research questions: 1. What are the concerns of WWVO regarding the N233 intersection Rhenen-Achterberg and can these concerns be objectified 2. How can the concerns of WWVO be objectively measured and what is the outcome? 3. Do the reconstruction proposals take into account the observed road (safety) problems and do these proposals meet the road safety requirements? Does the design of the new situation take into account possible red light violations, near misses, bicycle-bicycle conflicts, presence and violations of freight traffic, cycling speed from the Bergweg and driving speeds? What are the advantages and disadvantages of a grade-separated junction for a safe crossing? The study was carried out by conducting an extensive interview with members of WWVO and with the municipality of Rhenen to make an inventory of their concerns. In addition, traffic counts were carried out and camera footage was taken of the intersection to assess the concerns. A crash analysis was completed and a attitudinal survey was held among secondary school students and parents of children who have to cross the intersection. Finally, the design proposals of the province of Utrecht and WWVO were assessed. Concerns WWVO In an extensive interview with WWVO the project group revealed seven primary concerns about the current and future traffic situation at the intersection. These were (in no particular order): - Segregation effect resulting in changed travel patterns (called changed travel demand, resulting from fewer trips by bicycle, detours, trips accompanied by parents etc.) - red light violations - near-misses - bicycle-bicycle conflicts - freight transport - downhill cycling speed - driving speeds at the intersection. Crash analysis It should be noted that crash analyses use data from the police crash registration. Since 2010, the registration rate of the (injury) crashes has declined considerably in comparison with previous years. In addition, the registration rate of non-fatal crashes (and especially of crashes with material damage only) has always been low. Therefore it is very likely that the registered crash data for this location in the period after 2010 are even less complete than the registered data in the period before 2010. Consequently the number of (injury) crashes according to the registration is an underestimation of the actual number of crashes at the intersection. An analysis of the registered crashes in the period 2000-2013 shows that 33 crashes occurred during this period, 12 of which were injury crashes. The 18 casualties in these crashes sustained injuries ranging from minor injury to injury that required hospitalization. No fatal crashes occurred on the intersection during this period. Most crashes were side impacts or rear-end collisions. Passenger cars were the predominant mode involved in crashes (42 vehicles) and in a small number of cases they were slow traffic (one cyclist, one slow moped rider, and five moped riders). No crashes were recorded involving pedestrians. In a previous quick-scan, SWOV conducted an analysis on the crash data for the period 2001-2009. In this period 16 crashes were registered, 11 of which were injury crashes and none were fatal. The crashes in the period 2001-2009 present a slightly alarming picture. The intersection could be labelled a ' black spot ', depending on which years are considered and which definition of a black spot is applied (generally more than six injury crashes in three years). Due to the declining registration rate since 2010, it is unknown whether this location still could be regarded as a black spot. Changed travel demand The survey among (parents of) school-age children who have to cross the intersection shows that in the current situation few children make a detour because parents or children find the intersection unsafe (segregation effect). This is the case both for children in primary school as well as in secondary school. On the basis of the survey we estimate approximately 10% of trips are affected by the segregation effect of the intersection. Furthermore, the survey reveals that relatively more primary school children in the ages from 8 to 12 years old are accompanied (by parents or older children) when travelling to school than was found for Dutch children nationally. Also the age at which children travel to school independently is higher in Achterberg and environment than was found in the earlier Dutch study (10 years old in Achterberg vs 8 years old nationally). It is also noticeable that relatively many primary school children are brought to school by car. The number of children who walk to school is low and this is possibly due to the distance between home and primary school. The question of how children would be allowed to go to school if the intersection was to be provided with a grade-separated crossing facility (e.g. an overpass), shows a remarkable shift. In the age group of children of 4-7 years old, 23% would be allowed to cycle to school independently, compared to 2% in the current situation. Considering the big shift, this outcome is difficult to interpret. The data for children nationally reveal that children in this age group are generally escorted to school and do not travel independently. The same picture emerges for the 8-12-year-old primary school students. The shift is even bigger for this age group: the number of children that would be allowed to cycle independently would increase to as much as 88%, compared to 43% in the current situation. Once again this result does not match the national trend where the proportion travelling independently is much lower. Therefore the interpretation of this data must be done with some care: it is not certain that a grade-separated junction would actually result in such a big shift in travel patterns. However, it is clear that many parents would consider an alternative transport mode for their school-going children. Present traffic situation The traffic volumes on the main approaches of the intersection (in the direction of the crossing) are high: in the peak hours an average of about 650 motor vehicles per hour per approach. The volumes in the peak hours are close to the maximum capacity of the intersection. The traffic volumes on the minor approaches are considerably lower with a daytime average of about 160 motor vehicles per hour per approach. The ratio between traffic on the minor and major approaches is around 0.25. This is more favourable for road safety than a more equal distribution. Generally, the bicycle volumes are below 100 bicycles per hour (also during the peak hours) with the exception of the southern branch of the N233 in the morning peak (about 150 bicycles per hour). According to CROW standards bicycle volumes are considered relatively low, also during rush hours. Camera footage shows that in the current situation both cyclists and motor vehicles often ignore the red signal: on average one vehicle (cyclist or motor vehicle) per 34 minutes. Other offences were not as frequently observed at the current intersection. Illegal or incorrect overtaking, merging by motor vehicles and transverse crossing by cyclists sporadically occur. No bicycle-bicycle conflicts were observed, and neither were dangerous situations between buses and other traffic. The proportion of freight traffic on the N233 is between 5% and 10% and is low to normal in comparison with general volumes on similar provincial distributor roads. The average speed of motorized traffic on the N233 varies between 48 km/h and 74 km/h. The speed driven by 85% of the traffic, the so-called V85, varies between 65 km/h and 87 km/h. The average speed of the freight traffic is lower and the V85 of freight traffic does not exceed 80 km/h. The speed of cyclists on the Bergweg-West (downhill towards the junction with the N233) is about 23 km/h, which is higher than what CROW considers to be 'normal' (15-20 km/h). Assessment design proposals In general the design of a signalized intersection as proposed by the province meets the current design requirements for an intersection between a distributor road and an access road in rural areas. However, the proposed design can be improved. Due to the large speed differences (mainly between motorized traffic and cyclists/pedestrians) at the intersection, speed-reducing measures (such as a raised junction or speed humps on the approaches) are recommended. The speeds on the intersection should be limited to a maximum of 50 km/h. Enforcement using recognizable red light and speed cameras (set to a limit of 50 km/h) remains important. It is recommended that these camera’s cover both approaches of the N233; currently there is only one camera. The Bergweg-West is a 50 km/h distributor road and should have separate cycle paths. The detailed design should take into account a higher design speed for cyclists than the speed that is normally common for solitary moped/bicycle paths. This is especially the case for the downhill stretch towards the intersection with the N233. The bicycle facilities at the intersection should have an immediate connection with the bicycle facilities of the adjacent road section Bergweg-West. The proximity of the T-junction with Bergweg-East can lead to confusing traffic situations, especially for cyclists that use the Bergweg. The construction of a threshold treatment, a raised cycle path or even a raised junction should be considered. The sketch design of WWVO offers a grade-separated solution with a 3-arm roundabout. This proposal provides no insight into the layout of the intersections, the alignment and cross-sectional profile, and therefore this proposal was assessed at a sketch plan level. In the WWVO-design the traffic to and from Achterbergsestraatweg and Bergweg-East is redirected to a grade-separated intersection to the south of the current intersection. Bicycle traffic from the part of Rhenen situated at the southeast of the intersection, gets a new bicycle connection between the Boslandweg and Bergweg-West. For these cyclists this connection is shorter, more direct and, because of the grade-separated junction with the N233, safer than the current connection. The current intersection is converted to a 3-arm roundabout. This alternative offers a solution for a number of potential road safety problems on the intersection (especially lateral conflicts with intersecting traffic) but at the same time introduces new problems. For traffic from Achterberg this solution causes detours, whereby both cyclists and motorized traffic need to use a longer, indirect connection (a detour of about 400 metres). By diverting the traffic, the traffic volume on the Achterbergsestraatweg-West increases. This longer travel distance on an unsafer road type has negative road safety consequences. In this design, the road sections and intersections of the connections should be constructed in accordance with Sustainable Safety requirements. It must be investigated whether this solution is acceptable for the current road users. At locations where large volumes of slow traffic (for example, a main cycle route) cross a busy distributor road, it is advisable to construct a grade-separated bicycle or pedestrian bridge or tunnel. However, these are not evident at the intersection between the N233 and the Bergweg/ Achterbergsestraatweg. The road crash details (based on old data from 2001 to 2009) are slightly alarming, but not due to crashes involving vulnerable road users. Conflict-observations in the current situation do not present an alarming picture either. Therefore, a grade-separated solution does not seem warranted. Even with an increase in bicycle traffic, a grade-separated solution does not seem to be appropriate. Given the outcome of the survey, an increase in bicycle traffic is not likely and the number of cyclists will remain about the same, even with a new grade-separated bridge. Finally Due to high traffic volumes and large differences in speed, direction and mass, intersections and interchanges on through roads (always) have a grade-separated construction. Also within Sustainable Safety a grade-separated intersection is a unique predictability characteristic of a through road. Intersections on distributor roads (such as the N233) are generally at grade. At locations where large numbers of slow traffic (e.g. a main cycle route) cross a busy distributor road, it is recommended to construct a grade-separated bicycle or pedestrian bridge or tunnel. In the situation that was investigated here, large numbers of cyclists and pedestrians were not observed. Even taking into account an unlikely modal shift from the current supervised trip to school (mainly by car) to a future independent journey to school by bicycle, (such as the results of the survey suggest), volumes would still not warrant grade separation. A very common solution for this type of situation is an at-grade intersection, supported with median islands , speed reducing measures and, if necessary, a signalized intersection. A starting point of Sustainable Safety and the CROW Road Design Manual is that roundabouts are preferable at 4-arm intersections between 80 km/h distributor roads and 60 km/h access roads. However, this is subject to local conditions (capacity, space, integration and so on). If a roundabout is not feasible and traffic volumes allow it, a priority controlled intersection is the correct solution. If a roundabout is not feasible and traffic volumes are high, a signal controlled intersection is preferred, preferably in combination with speed reducing measures. The findings of the present study provide no reason to deviate from the CROW and SWOV-recommendations for intersections on rural distributor roads. The study takes into account the current and future traffic volumes on the intersection between the N233 and the Bergweg/Achterbergsestraatweg (including the relatively limited number of cyclists), the current level of road safety and the road safety level experienced by residents. To a large extent concurring with the plans of the Province, we recommend signal control with improved capacity and speed control measures for this intersection. This does justice to local environmental factors and to traffic and road safety elements. It is however recommended to monitor road safety and traffic behaviour on and near the intersection after the reconstruction. Furthermore, the main branches of the intersection must be equipped with speed-reducing facilities, supported by red light/speed camera's that are set to a limit of 50 km/h. The design should pay special attention to crossing cyclists, so that these are protected against conflicts with fast traffic both in time and in space. The Bergweg-West is a 50 km/h distributor road and should have separate cycle paths. For this approach (especially the downhill section in the direction of the N233) the higher speeds of cyclists should be taken into account in the detailed design. The bicycle facilities at the intersection must have a direct connection to the bicycle facilities of the adjoining road sections; this connection is now absent on the western branch. The proximity of the T-connection with the Bergweg-East can lead to confusing traffic situations, especially for cyclists that use the Bergweg. A solution in the form of a threshold construction, a raised bicycle path, or even a raised junction should be considered. The current number and type of crashes, the traffic situation (including conflicts) and the future traffic situation (especially the numbers of cyclists) at the intersection do not give rise to considering the construction of a grade-separated (bicycle or pedestrian) bridge or tunnel. This is subject to the condition that the above design improvements for the at-grade solution are applied.
Samenvatting