N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A F F T T N N a a t t i i o o n n a a l l R R o o u u n n May 2005 d d a a b b o o u u t t C C o o Principal Scientist, TRL n n f f e e r r Presented by Janet Kennedy e e n n c c e e 2 2 0 Accidents at roundabouts 0 0 0 5 5 D D R R A A F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 International review of design Review of Standard Consultation with practitioners Accident study Consider provision for non-motorised users Develop a hierarchical approach Revise Standard 0 0 0 0 5 5 • • • • • • • D D R R A A Project for UK Highways Agency on geometric design of roundabouts F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A F F T T A typical four-arm roundabout in the UK N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A F F T T A typical three-arm roundabout in the UK N N n circulatory a a o t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n Easier to construct Drainage More conspicuous central island No crown line c c e e 2 2 0 0 0 0 5 5 D D Emphasis on safety rather than capacity Roundabouts smaller than in UK Single or double lane designs Limited flaring Outward-sloping crossfall carriageway R R A A Review of design in other countries • • • • • F F T T N N a a t t i i o o n n n the UK a a i l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Typical crossfall F F T T £52,000 £78,800 £34,600 Average accident cost 8% N N 15% 14% 15% a a serious t t i i o o % fatal and n n a a l l R R o o u u n n d d a a b b o o No. of u u 85,000 18,700 111,000 214,000 £61,100 t t accidents C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A All roads Roundabouts Other junctions Non-junction F F T T Personal injury accidents in 2003 N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n junction accident injury accident f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D Higher flows / multiple lanes in the UK Difference in definition of: Cultural differences Main UK study is old (1984) Accident rates from current UK study are for high flow roundabouts only R R A A Differences between countries when comparing accidents at roundabouts • • • • • F F T T .23 .51 .77 0.1 1.5 0.6 0 0 1 Accident frequency 2.36 to 4.38 6 5 4 84 9 11 N N 290 1162 a a 12,000 t t i i o o Number of n n roundabouts a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c -arm only) e e 4 2 2 0 0 0 0 5 5 D D R R A A Comparison of accident frequencies (injury accidents per year) Country Australia France New Zealand UK (old – UK (current ) The Netherlands US F F T T ) r a e y r s pe N s N m t r a a n t t a e i i f o o d i n n o a c r a l c e l R R a b ( o o m y u u n n Nu nc d d a a ue b b q o o u e u r t t f C C o o nt 3456 n n f f de e e i r r c e e c n n A c c e e 2 2 6.0 4.0 2.0 0.0 0 0 y c n e u eq r f t n e cid c A 0 0 5 5 D D R R A A Accident frequency as a function of number of arms at the roundabout F F T T 9.3% 7.1% Severity 2.65 Dual cway roads N N a a t t i i o o n n a a l l R R o o 0.63 1.28 1.08 u u cway roads n n Single d d a a b b o o u u t t C C o o n n f f 326 649 e e sites r No. of r e e n n c c e e 2 2 0 0 0 0 5 5 3 4 D D R R arms No. of A A Accident frequency (injury accidents per year) by type of road F F T T 6 4 8 3 4-8 2-16 Rate 21-37 53-162 4 4 - - N N 4 8 11 179 182 a a t t i i o o Number of n n roundabouts a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n igh flow) f f e e h r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Australia France Germany (includes damage only) UK (old) UK (current – Sweden US Comparison of accident rates (injury accidents per 100 million vehicle-km) Country F F T T N N a a t t i i o ) o n n i a a G l l R R i o o g u u n ∑ n d d a a b b o o u u exp( t t C C β β 2 2 o o n n Q Q f f e e α α r r e e 1 1 α n n c c e e 2 2 0 0 0 0 5 5 A = kQ A = k Q A = k Q D D and layout variables: R R A A Accident models Accident frequency on each arm related to flow or These models were extended to include geometric F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D Entry path curvature (deflection) Entry width and approach Inscribed circle diameter Central island diameter Proportion of motorcycles Angle with next arm Approach curvature (Visibility) R R A A Variables affecting safety • • • • • • • • F F T T 0 9 6 3 20 1 25 100 ‘Conventional’ N N a a t t i i o o n n 0 8 4 7 a a 71 1 l l Small R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Single vehicle Approaching Entering-circulating Other vehicle Pedestrian Total 100 Percentage of injury accidents by type at 4-arm UK roundabouts F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 oach is downhill 0 0 0 0 5 5 D D Appr Problem with vehicles over shooting Danger of vehicle reaching motorway below R R A A North Lincolnshire roundabout Roundabout with single vehicle accident problem • • • F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R Circulatory carriageway cannot be seen Chevrons appear to be on splitter island People mark possible delineation effect of reflective marker posts A A Roundabout with single vehicle accident problem F F • • • T T .5 .0 9.3 9 8 7.1 22.6 1 Severity N N a a .8 t t 4.4 i i o 8.0 9.3 2 o 1 76.7 n n a a l l R R o o u u % of accidents n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e Cars 2 2 0 0 0 0 5 5 Pedestrians Vehicle type Motorcycles Pedal cycles D D R R A A % involvement by vehicle type F F Large goods vehicles T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e Low flow, compact design Underpass Cycle lane on roundabout Cycle path with crossings r r e e n n c c e e Relative involvement rate high Move against new roundabouts? Experienced v novice cyclists Cycles mix with other vehicles Cycle facilities 2 2 0 0 • • • • • 0 0 5 5 D D R R A A Pedal cyclists at roundabouts F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o in Calais with outer cycle path n n cyclist f f e e r r e e n n c c e e 2 2 mixes with traffic rides in centre of lane 0 0 0 0 5 5 D D Novice / cautious cyclist on outer cycle path Experienced R R A A • • F F T T Roundabout N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Cycle lane on circulatory carriageway F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A UK roundabout in York with cycle lane F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Eye-level view of UK roundabout in York with cycle lane F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 Splitter island Uncontrolled crossing (zebra) Signal controlled crossing Subway / overbridge Zebra crossing at 5 to 20m Signal controlled crossing at 20m or >60m 0 0 0 0 5 5 D D Small proportion of accidents (but high severity) Pedestrian facility Optimum location of crossing from roundabout Flaring and geometric delay R R A A Pedestrians at roundabouts • • • • F F T T stoke N N sing a a t t i i Ba o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A Pedestrian crossings at roundabouts F F T T Brent / Harrow N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 Long straight high speed approach Inadequate entry deflection Low circulating flow past an entry Excessive visibility to the right Significant tightening of turn radius partway round the roundabout Crown lines D D R R A A • • • • • • F F T T Overturning of large goods vehicles t urban a N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D New design hierarchy New compact design with single lane entry Greater emphasis on provision for non- motorised Allow outward-sloping crossfall roundabouts on single-carriageway roads At dual-carriageway roundabouts limit visibility to right until vehicles within 15m of give way line R R A A Possible changes to UK Standard • • • • • F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D Signalised roundabout with through traffic on main road across central island R R A A Hamburger (‘through-about’) F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D Signalised roundabout with through traffic on both roads across central island R R A A Hot cross bun (‘double-through-about’) F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o n n f f e e r r e e n n c c e e 2 2 0 0 0 0 5 5 D D R R A A A look back in time! F F T T N N a a t t i i o o n n a a l l R R o o u u n n d d a a b b o o u u t t C C o o Tel: +44 (0)1344 770953 n n Email: [email protected] f f e e r r Presented by Janet Kennedy e e End of Presentation n n c c e e 2 2 0 0 0 0 5 5 D D R R A A F F T T.