Road factors in multi and single vehicle motorcycle crashes in Queensland

1. Road factors in multi and single vehicle motorcycle crashes in Queensland Yusuf Adinegoro, Professor Narelle Haworth, Dr. Ashim Kumar Debnath Australasian Road Safety Conference (ARSC2015), Gold Coast, Thursday 15th October 2015

2. Rationale • In Queensland, number of motorcycles increased 8% per year between 2004-2011 (ABS,2015), motorcycles comprise 4% of all registered vehicles, but were involved in 13% of all fatal crashes (TMR, 2015) • Motorcycles have higher crash risk due to being more sensitive to road surface conditions and road geometry (ACEM, 2004) • Single Vehicle (SV) – hit fixed or temporary object or fall from vehicle - road geometry and road surface defects are more common (Hurt et al., 1981; Saleh et al., 2010; Shankar & Mannering, 1996) • Multi-Vehicle (MV) - involved another vehicle - intersections, merging, turning areas, and mid-block locations are common (ACEM, 2004; Haque, Chin, & Debnath, 2012) MV SV

3. MV and SV crash locations Queensland South East Queensland (72%) North Coast and Wide Bay/Burnett (21%) 47% 53% Metropolitan Region (34%). 68% 32% South Coast (17%) 57% 43%

4. Crash Trends Multi-vehicle (MV) and Single-vehicle (SV) motorcycle crashes in Queensland 2004-2011 -9% -5%

5. Methodology Data Variables Analysis Police reported crashes • Binary Logistic Model • Response variable: MV=1, SV=0 • Year • Crash month • Day of week • Time period • Speed limit zone • Lighting condition • Horizontal alignment • Vertical alignment • Road surface condition • Traffic control type • Crash severity • Atmospheric condition 1 January 2004 – 31 December 2011 Property damage only (PDO) excluded n=12,657 SV : 43% MV : 57%

6. Results

7. Horizontal Road Geometry Findings SV crashes were more likely to occur on curves both viewed- obscured (218% higher odds) and curved-view open (230% higher odds) than MV Previous Findings • Horizontal curves influenced the frequency of SV (Schneider et al. 2010). • SV on rural roads have higher likelihood to fatal than urban (Saleh et.,al 2004) • A decreasing radius curve was considered to be a danger to riders (ACEM 2004).

8. Vertical Road Geometry Finding SV crashes were more likely to occur on grade gradients (19% higher in odds) than MV crashes Previous Findings • Descending gradients identified as critical in both MV and SV (Saleh et al., 2010). • Deceleration rate under braking creates wobble (Limebeer et al., 2001), • Wobble most common loss of control mode in SV (Hurt et al. (1981).

9. Road Surface Finding SV crashes were more likely to occur on sealed-wet roads (112% higher odds) than MV crashes Previous Findings • Inability to control motorcycles on rough road surface (Haworth, 1997) • Slippery surfaces often lead to causing out-of-control (Hurt 1981). • In non motorcycle study, wet pavement was found to be a significant factor in crashes (Caliendo et al., 2007). • Riders are likely to reduce speed as they compensate the risk of riding when the road surface is wet (Quddus et al., 2002).

10. Conclusion • Road geometric factors (horizontal and vertical alignment) and road surface factors (sealed/unsealed and wet/dry) were more important in SV than MV crashes • Confirms international research findings regarding the greater role of road infrastructure factors in SV crashes • Need to improve road infrastructure safety and provide appropriate treatment to reduce the occurrence and severity of motorcycle crashes • Further research will be undertaken to estimate the contribution of road factors by collecting more detailed information or road design & road surface