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Oliver carsten institute of transport studies leeds univ

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  • 1. Institute for Transport StudiesLower speeds and Intelligent SpeedAdaptation: what do they deliver forsafety and CO2?Oliver CarstenInstitute for Transport StudiesUniversity of Leeds
  • 2. The evidence base: two projectsISA-UK (2000-2006) CfIT ISA (2007-2008)
  • 3. Terminology• Advisory ISA: Informs the driver of the speed limit and warns the driver when the limit is being exceeded (= enhanced SatNav)• Voluntary (or Overridable) ISA: The information on speed limit is linked to the vehicle’s engine management system and perhaps additionally to the braking system — the system comes on with the vehicle ignition, but it may be overridden by the driver at will• Mandatory ISA: Works like Voluntary ISA, but without the option to override
  • 4. Our vehicles• Voluntary system that 30 30 limited speed to the prevailing limit (no acceleration beyond limit)• Drivers could override at will• Vibration on throttle pedal to prevent over- throttling
  • 5. Some of our fleet in the ISA-UKproject
  • 6. Field trial timingsTrial 1Trial 2Trial 3Trial 4 0 2004 12 2005 24 2006 36
  • 7. The ISA field trials database• Driving by 79 drivers over 6 months – 1 month without ISA (baseline) – 4 months with Voluntary ISA – 1 month with ISA again off• Total mileage: 429,487 – With speed limit information: 354,592 – For ISA active phase: 218,790 – All at 10Hz
  • 8. Speed profile by time on 30 mphroads 20% Mandatory Mandatory 18% Voluntary Voluntary Baseline 16% Baseline 14% Proportion of journey 12% 10% 8% 6% 4% 2% 0% 0 10 20 30 40 50 60 70 80 90 100 Vehicle speed (mph)
  • 9. Safety
  • 10. Accident prediction and cost-benefitanalysis (latest version) “Recipe”: • Predict traffic growth (DfT advice) • Predict accident trends without ISA • Predict additional safety impact of ISA (via observed change in speed patterns) – Depends on ISA type and road type • Analyse costs and benefits over 60 years from 2010 • Scenario-based approach
  • 11. Method for estimating accidentreductions with ISA• Based on models from the literature of relationships between speed and 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
  • 12. Use of data from ISA field trials toprovide speed profiles Phase 1 Phase 2 Phase 3 Without With Without 1 month 4 months 1 monthBaseline: data collected from Phase 1 (i.e. no ISA)Voluntary ISA: data collected from Phase 2 (i.e. the ISA system wasoverridable)“Mandatory” ISA: data collected from Phase 2 excluding when ISA wasoverridden
  • 13. Estimated impact of Advisory ISA onspeed• Obtained from: Shift from Baseline (no ISA) to Voluntary ISA x Adjustment factor from LAVIA trial in France, i.e. LAVIA Advisory speed reduction ——————————————— LAVIA Voluntary speed reduction
  • 14. Predicted risk reduction by typeof ISA Reduction in Injury Accidents with ISA ISA Variant Overall Reduction Advisory ISA −2.7% Voluntary (Overridable) ISA −12.0% Mandatory (Non-Overridable) ISA −28.9%
  • 15. Emissions
  • 16. Emissions modelling using recordedspeeds from ISA-UK trialsDone two ways:1.With detailed second-by-second GAMs models2.With more aggregated speed-emissions curves
  • 17. Input into GAMs Driving on 70 mph roads  Baseline Driving Driving with ISA Engaged Counts 76121 10 37706 18677 9252 5 4583 acceleration (km/h/s) 2270 1124 557 0 276 137 68 34 -5 17 8 4 -10 2 1 0 50 100 150 0 50 100 150 speed (km/h)
  • 18. CO2 emissions from UK field trialspeed profilesGAMs modelling Speed-emissions curves Speed Change with Change with Change with Limit Voluntary ISA Mandatory Speed Limit Mandatory (mph) ISA (mph) ISA 20 0.0% +0.1% 30 +2.8% 30 −0.4% −0.4% 40 +2.8% 40 −1.2% −1.2% 60 +0.4% 60 +0.3% +0.3% 70 −4.2% 70 −3.4 % −5.8%
  • 19. Network micro-simulation modelling• 4 networks: 1. Rural – A614 2. Urban – Sheffield S10 3. Urban – Sheffield Sheaf Valley 4. Motorway – A1(M) near Gateshead• AIMSUN micro-simulation model modified to cater for Voluntary ISA• For emissions, used speed-emissions curves
  • 20. Critical mass effect?   Urban – All vehicles Urban – Cars Urban – HGVs 25 25 14 12 20 20 10 % Speeding % Speeding % Speeding 15 15 8 10 10 6 4 5 5 2 0 0 0 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100   Rural – All vehicles Rural – Cars Rural – HGVs 4 5 80 70 4 3 60 % Speeding % Speeding % Speeding 3 50 2 40 2 30 1 20 1 10 0 0 0 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100   Motorway – All vehicles Motorway – Cars Motorway – HGVs 10 12 6 8 10 5 % Speeding % Speeding % Speeding 8 4 6 6 3 4 4 2 2 2 1 0 0 0 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
  • 21. The future(s)
  • 22. Predicted ISA penetration under the MarketDriven scenario 100%Proportion of ISA systems in veh fleet 90% 80% 70% 60% Voluntary 50% Advisory 40% Non‐ISA 30% 20% 10% 0% 2010 2020 2030 2040 2050 2060 2070
  • 23. Predicted ISA penetration under the Authority Driven scenario 100%Proportion of ISA systesm in veh fleet 90% 80% 70% 60% Mandatory 50% Voluntary 40% Advisory 30% Non‐ISA 20% 10% 0% 2010 2020 2030 2040 2050 2060 2070
  • 24. Crash reduction over time forMarket Driven ISA   1 Fatal 0.9 Serious Accident reduction rate 0.8 Slight 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2010 2020 2030 2040 2050 2060 2070
  • 25. Crash reduction over time forAuthority Driven ISA   1 Fatal 0.9 Serious Accident reduction rate 0.8 Slight 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2010 2020 2030 2040 2050 2060 2070
  • 26. Predicted safety outcomes Crashes Saved 2010 to 2070 Slight Crashes Serious Crashes Fatal CrashesMarket Driven 4% 8% 13%Authority Driven 15% 25% 30%
  • 27. Predicted environmental outcomes Savings in emissions and fuel 2010 to 2070 CO2 Fuel (tonnes x 106) (litres x 106) Market Driven 4.139 6,460 Authority Driven 16.303 25.436
  • 28. Source of ISA benefits over 60-yearperiod ISA Benefits (£1m) % Due toImplementation AccidentScenario Fuel CO2 Accidents TOTAL SavingsMarket Driven £446 £196 £32,808 £33,450 98%Authority Driven £1,740 £773 £85,122 £87,636 97%
  • 29. Do the benefits outweigh the costs?• Benefit to cost ratios (accidents + fuel + CO2): – Market Driven scenario 3.4 – Authority Driven scenario 7.4
  • 30. Conclusions• The safety benefits of ISA are very considerable• The harder the push for ISA and the “stronger” the system, the greater the benefits• The environmental benefits of ISA are real – There may be benefits on roads other than 70 mph roads• In cost-benefit terms the environmental impact is much less than the safety impact• Much of the potential of ISA, e.g. to replace traditional and costly traffic calming, was not counted
  • 31. Thank you for your attention!o.m.j.carsten@its.leeds.ac.uk