SAFETY CONSIDERATIONS FOR THE CROSS- SECTION DESIGN OF 80 KM/H RURAL ROADS IN THE NETHERLANDS Jan Hendrik van Petegem Govert Schermers Paper ID 36

OVERVIEW Road safety context Safety aspects related to cross-section design Design practice and guidelines Recommendations 2 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

DUTCH SITUATION - CRASHES PER ROAD TYPE 3 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands Acces Roads Distributor Roads Through Roads

DUTCH SITUATION - RURAL 80KM/H ROADS CRASH TYPES 4 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

ROAD DESIGN GUIDELINES Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands Foundation for a safe road design Not legally binding Technical specifications are –Based on laws of physics –Less often based on the relation with crash numbers / crash severity –Allowing a wide window of minimum and preferred specifications Safety effects of design choices are not made explicit

CONSIDERED CROSS-SECTION ELEMENTS RELATING ROAD SAFETY Roadway Traffic lanes Shoulder Directional/median separation Safety zone 6 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

7 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands TYPICAL CROSS SECTION OF SCW 80KM/H ROADS x x

8 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands ROADLANE WIDTH Dutch roadlane widths seem small –Considering the travelled way and width of trucks and cars –Comparing internationally x x

9 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands ROADLANE WIDTH Traffic lane width [m] United StatesNew ZealandAustralia x x

10 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands SHOULDER WIDTH Narrow paved shoulders ( 1m)  Wider paved shoulders are 33% safer No effects of semi hardend shoulders were found x x

11 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands ROADWAY WIDTH Australian research 10m vs 8m : factor m vs 7m : factor m vs 7m : factor 1.2 US Research m vs m : factor x x

12 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands DRIVING DIRECTION/Median SEPARATION Double centreline with a vertical element –Can reduce/eliminate illegal overtaking Flush median or double centreline of 1m+ –20-50% crash reduction x x

13 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands DRIVING DIRECTION SEPERATION Median width comparison 3m to 30m –Factor 0.73 for all crashes –Factor 0.25 for median crossings x x Cable barrier (2+1, with a majority of head on crashes) –80% crash reduction of fatal crashes –50% crash reduction severe injury crashes

14 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands SAFETY ZONE x x Dutch research – 2m: factor 1.5m –In Depth research : A small safety zone in 50% of all crashes US Research –<1m vs 5m : 22% safer –5m vs 9m : 44% safer

15 Widening the roadway, traffic lane, shoulder and safety zone are all related to higher safety levels However: Widening the view increases speeds driven Increases in speeds are related to higher crash severities Jan Hendrik van Petegem INCREASING CROSS-SECTIONS vs HIGHER SPEEDS Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

16 Safety factors found and shown are single effects The effects of confounding factors are unknown Safety effects shows the direction and importance of safety measures The effect of combined safety measures are however mostly unknown Jan Hendrik van Petegem COMBINATION OF EFFECTS Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

RECOMMENDATIONS ON THE CROSS SECTION DESIGN FOR UNDIVIDED RURAL 80km/H ROADS WITH A NARROW RIGHT OFF WAY Safety zone –Removal of obstacles –Screening off obstacles –Introduction of semi-hard shoulders Driving separation –Application of a median –Application of a cable barrier –Application of a double centre line marking of more than 1m wide including a difficult to cross element 17 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

Preferred Roadway delineation –Roadway width9.5m –Lane width3.3m –Directional separation1.4m including cable barrier –Paved Shoulder0.6m Standard Roadway delineation –Roadway width7.5m –Lane width2.75m –Directional separation1.1m –Paved Shoulder0.3m 18 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands RECOMMENDATIONS ON THE CROSS SECTION DESIGN FOR UNDIVIDED RURAL 80km/H ROADS WITH A NARROW RIGHT OFF WAY

RECOMMENDATIONS FOR CHANGING THE NATURE OF DESIGN GUIDELINES Improve awareness of design impact on road safety Support safe road design decision making Show evidence based relations between design and road safety Develop a reference safety level for comparison of safety levels 19 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

20 Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands

21 Road designs are restricted by Budget Available space –Historical development –Landscape integration : Canals for drainage and irrigation Land use density Tree lining prevalence Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands ROAD DESIGN PRACTICE

22 Foundation for a safe road design Foundation for the guidelines is a Sustainable Safety Approach Technical specifications are –Based on laws of physics –Less often based on the relation with crash numbers / crash severity Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands ROAD DESIGN GUIDELINES

23 The use of guidelines are effected by Minimum and recommended requirements –Combination of minimum requirements Guidelines are not legally binding –Deviations are allowed Safety effects of design choices are not explicitly mentioned –Consequences of design choices are unclear/unknown/old Jan Hendrik van Petegem Safety considerations for the cross-section design of 80km/h rural roads in the Netherlands ROAD DESIGN PRACTICE AND GUIDELINES