The safety problem: nature of the problem, extent (partially covered already), factors

1. The safety problem: nature of the problem, extent (partially covered already), factors CE 552 week 4

2. Hauer Philosophy • You can learn the effect of a safety treatment with before and after observation – wrong • You have to have true randomized experiments to learn anything – wrong • You can learn from experience – ok • You must take great care in doing so – ok • You shouldn’t experiment – wrong • “the only way to find out what will happen when a complex system is disturbed is to disturb the system, not merely to observe it passively” – Box 1966

3. Hauer Philosophy • Opportunities abound • If we do evaluate, we do so “in-house” because there is risk of failure • We do not publish because the measure failed • What is needed … • Sound methodologies • Collective will to employ them properly

4. Hauer quotes • “Perhaps we transportation engineers can not act in good faith as the custodian of traffic safety because the goal of safety and efficiency are too often in conflict” • “Within limits, highway traffic engineers can make roads safer or less safe so we must know the safety repercussions of our choices”

5. Road Safety Defined (From a Science-based Perspective) • Improved “security” may decrease “safety” • Accident or crash? • Is safety the number of crashes per time? What if some days have no crashes – perfectly safe? • Use running average? • Use longer period of time? • Safety may change – must be allowed to • Requires use of statistics (expected values) and reliability during a specific period • Counts are a “hint” at the underlying numbers

6. Federal Transportation Goals • Safety • Old: reduce fatality rate to 1.0 • New: ??? • Congestion • Preservation • Environment

7. Effect of Crashes on Traffic Congestion and Travel Reliability http://ops.fhwa.dot.gov/congestion_report/executive_summary.htm Notes: Cambridge Systematics study shows that the costs of traffic crashes is nearly two and half times the cost of congestion – $164.2 billion for traffic crashes and $67.6 billion for congestion

8. Economic cost of crashes • value of life (FHWA Iowa division memo): $5.8million? • Iowa uses: • http://www.iowadot.gov/traffic/tsip/tsipB-C.xls • “You'll see that we've sold out...errrrrr...begun to use the Federal numbers in our B/C analyses for TSIP (and probably other things).” MDP • “For SICL, DOT uses 200, 100, 10, 1 and not actual $$$.  PDO for SICL is included via frequency and rate so thus no need to replicate via severity index.” MDP

9. Evans’ thoughts • “Factors” rather than “cause” (contributing circumstances) • Is it safer to keep a pet crocodile than a pet dog? – how to answer this?

12. Human Factors • Driver intelligence/skill • ladder in car • Des Moines drivers • Reaction time tests http://www.bbc.co.uk/science/humanbody/sleep/sheep/reaction_version5.swf • Distractions • docs\text_messaging_crash.mht • Distracting Miss Daisy (includes risk compensation) • Cell phone bill; KCCI report • Speeding • Why the EZ pass speed is 15 mph • Fricker p. 307 “think about it”

13. NCHRP 500 • aggressive driving http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_500v1.pdf • unlicensed drivers http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_500v2.pdf • seat belts http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_500v11.pdf • Drowsy/distracted http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_500v14.pdf • Alcohol http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_500v16.pdf

14. Road Crash Factors • http://www.collegehumor.com/video:1754304