Natiionall Roundabout Conference 2005 DRAFT 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 Accidents at roundabouts f e e r r e e n n c c e e
2 2 0 Presented by Janet Kennedy 0 0 0 5 5
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Principal Scientist, TRL R R A A F F T May 2005 T Project for UK Highways Agency on N geometric design of roundabouts N a a t t i i o o n n a a l l
R • International review of design R o o u u n n d • Review of Standard d a a b b o o u • Consultation with practitioners u t t
C C o o n • Accident study n f f e e r r e e n n
• Consider provision for non-motorised c c e e
2 users 2 0 0 0 0 5 5
D • Develop a hierarchical approach D R R A A F • Revise Standard 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 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 Review of design in other countries N N a a t t i i o o n n a a l l
R • Emphasis on safety rather than capacity R o o u u n n d • Roundabouts smaller than in UK d a a b b o o u • Single or double lane designs u t t
C C o o n • Limited flaring n f f e e r r e e n n
• Outward-sloping crossfall on circulatory c c e e
2 carriageway 2 0 0 0 0 5
Easier to construct 5
D Drainage D R R A A
More conspicuous central island F F T No crown line T Typical crossfall 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 Personal injury accidents in 2003 N N a a t t i i o o n n a a l l
R No. of % fatal and Average R o o u accidents serious accident cost u n n d d a a b b o All roads 214,000 15% £61,100 o u u t t
C C o o n n f f e Roundabouts 18,700 8% £34,600 e r r e e n n c c e e
2 Other junctions 111,000 14% £52,000 2 0 0 0 0 5 5
D D R Non-junction 85,000 15% £78,800 R A A F F T T Differences between countries when N comparing accidents at roundabouts N a a t t i i o o n n a a l l
R • Higher flows / multiple lanes in the UK R o o u u n n d • Difference in definition of: d a a b b o o u junction accident u t t
C C o o n injury accident n f f e e r r e e n n
• Cultural differences c c e e
2 2 0 • Main UK study is old (1984) 0 0 0 5 5
D D R • Accident rates from current UK study are for R A A F high flow roundabouts only F T T Comparison of accident frequencies N (injury accidents per year) N a a t t i i o o n n a a l l
R R o Country Number of Accident o u u n n
roundabouts frequency d d a a b b o Australia 290 0.6 o u u t t
C France 12,000 0.1 C o o n n f f e e r
New Zealand 95 0.51 r e e n n c c e UK (old – 4-arm only) 84 2.36 to 4.38 e
2 2 0 0 0 UK (current ) 1162 1.77 0 5 5
D D
The Netherlands 46 0.23 R R A A F F
US 11 1.5 T T Accident frequency as a function of N number of arms at the roundabout N a a t t i i o o n n a a l l
R Accident frequency (accidents per year) R o o u u n n d d a 6.0 a b b o o y u u c t t
n
C C e o o u 4.0 n n f f eq e e r r r f e e t n n n c c e 2.0 e e
2 2 cid 0 c 0 0 0 A 5 5
0.0 D D R 3456 R A A F F T Num be r of ar m s T Accident frequency (injury accidents N per year) by type of road N a a t t i i o o n n a a l l
R R o o u
No. of No. of Single Dual Severity u n n d arms sites cway cway d a a b b o roads roads o u u t t
C C o o n n f
3 326 0.63 1.28 9.3% f e e r r e e n n c c e e
2 2 0 4 649 1.08 2.65 7.1% 0 0 0 5 5
D D R R A A F F T T Comparison of accident rates (injury N accidents per 100 million vehicle-km) N a a t t i i o o n n a a l l
Country Number of Rate R R o o u
roundabouts u n n d d a Australia - 4-8 a b b o o u France 179 4 u t t
C C o o n
Germany - 53-162 n f f e e
(includes damage only) r r e e n n c UK (old) 84 21-37 c e e
2 2 0 UK (current – high flow) 44 36 0 0 0 5 5
D Sweden 182 2-16 D R R A A
US 11 8 F F T T Accident models N N a a t t i i o o n n a a l l
R Accident frequency on each arm related to flow R o o u α u n A = kQ n d d a a b b o or o u u t t
C α β C
A = k Q Q o 1 2 o n n f f e e r r e e n n c These models were extended to include geometric c e e
2 2 0
and layout variables: 0 0 0 5 5
D D R α β R A A = k Q1 Q2 exp( ∑gi Gi ) A F F T T Variables affecting safety N N a a t t i i o o n n a a l l
R • Entry path curvature (deflection) R o o u u n n d • Entry width and approach width d a a b b o o u • Inscribed circle diameter u t t
C C o o n • Central island diameter n f f e e r r e e n n
• Proportion of motorcycles c c e e
2 2 0 • Angle with next arm 0 0 0 5 5
D D R • Approach curvature R A A F F T • (Visibility) T Percentage of injury accidents by N type at 4-arm UK roundabouts N a a t t i i o o n n a a l l
Small ‘Conventional’ R R o o u u n n d Single vehicle 8 30 d a a b b o o u u t Approaching 7 25 t
C C o o n n f f e Entering-circulating 71 20 e r r e e n n c c e Other vehicle 10 19 e
2 2 0 0 0 0 5 Pedestrian 4 6 5
D D R R A Total 100 100 A F F T T Roundabout with single vehicle N accident problem N a a t t i i o o n n a a l l
• Approach is downhill R R o o u u n • Problem with n d d a vehicles over a b b o o u
shooting u t t
C C o • Danger of vehicle o n n f f e reaching motorway e r r e e n
below n c c e e
2 2 0 0 0 0 5 5
D D R R A A F F T T
North Lincolnshire roundabout Roundabout with single vehicle N accident problem 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 • Circulatory carriageway cannot be seen R A A F F T • Chevrons appear to be on splitter island T • People mark possible delineation effect of reflective marker posts % involvement by vehicle type N N a a t t i i o o n n a a l l
R
Vehicle type % of accidents Severity R o o u u n n d d a Pedal cycles 8.0 9.5 a b b o o u u t t
C Motorcycles 14.4 19.3 C o o n n f f e e r r e Large goods vehicles 9.3 8.0 e n n c c e e
2 2 0 Cars 76.7 7.1 0 0 0 5 5
D D R Pedestrians 2.8 22.6 R A A F F T T Pedal cyclists at roundabouts N N a a t t i i o o n n a a l • Relative involvement rate high l
R R o o u u
• Move against new roundabouts? n n d d a a b b
• Experienced v novice cyclists o o u u t t
C • Cycles mix with other vehicles C o o n n f
Low flow, compact design f e e r r e e n n c
• Cycle facilities c e e
2
Underpass 2 0 0 0 Cycle lane on roundabout 0 5 5
D Cycle path with crossings D R R A A F F T T Roundabout in Calais with outer cycle path 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
• Novice / cautious cyclist on outer cycle path D D R R A • Experienced cyclist A F F T mixes with traffic T rides in centre of lane Cycle lane on circulatory carriageway 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 UK roundabout in York with cycle lane 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 Eye-level view of UK roundabout in York N with cycle lane 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 Pedestrians at roundabouts N N a a t t i i o o n n a a l l
R • Small proportion of accidents (but high severity) R o o u u n n d • Pedestrian facility d a a b b o
Splitter island o u u t t
Uncontrolled crossing (zebra) C C o o
Signal controlled crossing n n f f e e r
Subway / overbridge r e e n n c c e • Optimum location of crossing from roundabout e
2 2 0 0
Zebra crossing at 5 to 20m 0 0 5 5
D
Signal controlled crossing at 20m or >60m D R R A A F • Flaring and geometric delay F T T Pedestrian crossings at roundabouts 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 Brent / Harrow 2 0 0 0 0 5 5
D D R R A A F F T T
Basingstoke N Overturning of large goods vehicles N a a t t i i o o n n a a l l
R • Long straight high speed approach R o o u u n n d • Inadequate entry deflection d a a b b o o u • Low circulating flow past an entry u t t
C C o o n • Excessive visibility to the right n f f e e r r e e n n
• Significant tightening of turn radius partway c c e e
2 round the roundabout 2 0 0 0 0 5 5
D • Crown lines D R R A A F F T T Possible changes to UK Standard N N a a t t i i o o n n a a l l
R • New design hierarchy R o o u u n n d • New compact design with single lane entry d a a b b o o u • Greater emphasis on provision for non- u t t
C C o motorised o n n f f e e r r e • Allow outward-sloping crossfall at urban e n n c c e roundabouts on single-carriageway roads e
2 2 0 0 0 0 5 • At dual-carriageway roundabouts limit visibility 5
D D R to right until vehicles within 15m of give way R A A F line F T T Hamburger (‘through-about’) 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
Signalised roundabout with through traffic on main road across central island Hot cross bun (‘double-through-about’) 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
Signalised roundabout with through traffic on both roads across central island A look back in time! 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 d d a a b b o o u u t t
C C o o n n f End of Presentation f e e r r e e n n c c e e
2 2 0 Presented by Janet Kennedy 0 0 0 5 5
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Tel: +44 (0)1344 770953 R R A A F F T Email: [email protected] T