intelligent speed assistance: why do we need it? · 2014. 12. 4. · “speed remains a very...
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Institute for Transport Studies
Intelligent Speed Assistance: Why Do We Need It? Oliver Carsten Institute for Transport Studies University of Leeds UK
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Speed
“Speed remains a very important risk factor. It has a greater effect on the number of accidents and injury severity than almost all other known risk factors.” Rune Elvik, The Power Model of the relationship between speed and road safety: Update and new analyses (2009)
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We know a lot about speed and risk
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Severity: the power model Andersson and Nilsson,1997; Nilsson, 2004; Elvik et al., 2004; Elvik, 2009; Elvik, 2013:
– Injury accidents go up approximately with the proportionate change in speed squared for a length of road
– Serious injury accidents approximately with speed cubed
– Fatal accidents approximately with speed to the fourth power Source: Nilsson, 2004
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UK On-the-Spot Data: Collision speed and the risk of car driver death in frontal collisions
Source: DfT, 2010 (dashed lines show 95% confidence interval)
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Impact speed and the risk of pedestrian death
Source: DfT, 2010 (dashed lines show 95% confidence interval)
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Collision speed and the risk of car driver death in side collisions
Source: DfT, 2010 (dashed lines show 95% confidence interval)
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Real-world trials
isa
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Denmark (2000-2001 and 2005-2008) Finland (2001-) ISA-UK (2001-2006) Two projects in Belgium (2001-2002) LAVIA in France (2002-2006) Austria (2003-2004) Norway (2005-?) + Australia (TAC SafeCar and NSW) Canada Japan (Soft Car)
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Assisting ISA: effect on behaviour and attitudes
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The ISA-UK trials 2 urban trials (1 private motorists, 1 fleet)
2 rural trials (1 private motorists, 1 fleet)
79 drivers with a mix of: Younger / older Male / female Speeding intenders / non-intenders
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An overridable assisting system
• System that limited speed to the prevailing limit (no acceleration beyond limit)
• Drivers could override at will
• Vibration on throttle pedal to prevent over-throttling
30 30
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Speed distribution on 30 mph (50 km/h) urban roads
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Vehicle Speed (mph)
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Phase 1 Phase 2 Phase 3Before During After
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Speed distribution on 70 mph (110 km/h) roads
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Vehicle Speed (mph)
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(%)
Phase 1 Phase 2 Phase 3Before During After
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Acceptability
-2
-1
0
1
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Time 1 Time 2 Time 3 Time 4
Mea
n Sc
ore
UsefulnessSatisfaction*
Before After Early with
Late with
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Intention
Mean intention to speed
At start of trial At end of with ISA period At end of after period
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Impact Prediction
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Method for estimating accident reductions with ISA
• Based on models from the literature relating speed to crash risk (e.g. Kloeden et al., 2001, 2002)
• These models have been calculated from real-world data
• They are not drawn from the police reported contributory factors for accidents
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Estimated risk reduction by type of ISA
Estimated Reduction in Injury Accidents for Vehicles with ISA
ISA Variant Reduction
Advisory ISA −2.7%
Assisting (Overridable) ISA −12.0%
Assisting (Non-Overridable) ISA −28.9% = −50% for fatal crashes
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What is the importance of regulation?
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GB accidents saved over time for under the Market Driven scenario
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2010 2020 2030 2040 2050 2060 2070
Accid
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rate
FatalSeriousSlight
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GB accidents saved over time for the Authority Driven scenario
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2010 2020 2030 2040 2050 2060 2070
Accid
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FatalSeriousSlight
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Comparison of predicted outcomes
• Benefit to cost ratios (accidents + fuel + CO2):
– Market Driven scenario 3.4
– Authority Driven scenario 7.4
Note that we used rather high numbers for costs
Slight Crashes Serious Crashes Fatal Crashes Market Driven 4% 8% 13% Authority Driven 15% 25% 30%
GB Crashes Saved from, 2010 to 2070
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Interpretation of scenario analysis
• Both scenarios are winners
• The harder the push for ISA and the “stronger” the system, the greater the benefits
• Shows the importance of regulation
• Much of the potential of ISA, e.g. to replace traditional and costly traffic calming, was not counted
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Confirmation from Norway
Vaa et al. (2014) examined the safety potential for Norway of a number of driver assistance systems, including Adaptive Cruise Control, alcolocks, seatbelt reminders, Electronic Stability Control and fatigue warning.
Their conclusion was:
“The most effective driver support system is ISA.”
Similar conclusions are being reached by the current review of the General Safety Regulation of motor vehicles for the European Commission.
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Conclusions
• ISA is a well-proven technology with very significant safety benefits
• Regulation is necessary to maximise the impact of ISA on traffic injuries and deaths
• Requirement of the overridable assisting system provides a sensible way forward