MICHIGAN VEHICLE CODE (EXCERPT)

Transcription

1 Tra affic Saffety Ana alysis: Frm Find F ing The e Prble em T T Fix xing It S Student t Wrkbk and d Class Referenc R ce July 2008 Lcal Techn nical Assistance Prgram m 309 Dillman n Hall Michigan Te echnlgical University Hughtn, MI M

2 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Mdule 1: Overview f Yur Crash Data NOTES: MICHIGAN VEHICLE CODE (EXCERPT) Sec Reprt f accidents resulting in death, persnal injury, r prperty damage; frms; analysis; use; retentin. The driver f a mtr vehicle invlved in an accident that injures r kills any persn, r that damages prperty t an apparent extent ttaling $1, r mre, shall immediately reprt that accident at the nearest r mst cnvenient plice statin, r t the nearest r mst cnvenient plice fficer. The fficer receiving the reprt, r his r her cmmanding fficer, shall immediately frward each reprt t the directr f the department f state plice n frms prescribed by the directr f the department f state plice. The frms shall be cmpleted in full by the investigating fficer. The directr f the department f state plice shall analyze each reprt relative t the cause f the reprted accident and shall prepare infrmatin cmpiled frm reprts filed under this sectin fr public use. A cpy f the reprt under this sectin and cpies f reprts required under sectin 621 shall be retained fr at least 3 years at the lcal plice department, sheriff's department, r lcal state plice pst making the reprt.00 f 1949 UD 10 frms: The UD 10 Traffic Crash Reprt is used in the State f Michigan by plice agencies t reprt all traffic related mtr vehicle crashes. The frm is als used t recrd any crash invlving a snwmbile r ff rad vehicle (ORV), whether traffic r nn traffic related. Crash Severity Scale Natinal Safety Cuncil KABCO Scale: K Fatal Injury A Incapacitating Injury B Nn incapacitating Injury C Pssible Injury O N Injury MALI Michigan Accident Lcatins Index: Linear referencing system that is a table f all public rads by cunty and city that lists their start pint and mileage t intersectins including the name f the crss street. Crash Lcatin: In Michigan all crash reprts are sent t the Michigan State Plice Criminal Justice Center in Lansing, MI where they are checked and physically lcated using the On Frm lcating system which references crash lcatins frm the nearest knwn intersectin. Example In the City f Hughtn, n Sheldn Ave (US 41), 120 feet west frm the intersectin f Ddge Street. Abut 70 t 80 percent f all crashes aut lcate using this data, the remaining crashes need t reviewed by a technician. Page 2 f 25

3 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Michigan Crash Types: The Michigan State Plice have 10 basic crash types. MDOT expands these 10 basic crash types t 27 crash types based n circumstances surrunding the crash. Example MSP has right angle as a crash type, MDOT expands this t angle straight, angle drive and angle turn. Crash Type Determinatin: Crash Type is based n the intended directin f travel, regardless f pint(s) f impact r directin vehicles ultimately face after crash. Damage area n the vehicle alne des nt determine crash type UD 10 manual p.17 FOIA f Crash Data: 23 U.S.C. 409 ( Sectin 409 ) was enacted t address this cncern. This law expressly frbids the discvery r admissin int evidence f reprts, data, r ther infrmatin cmpiled r cllected fr activities required pursuant t several Federal highway safety prgrams (Sectins 130, and 152 (nw 148)), r fr the purpse f develping any highway safety cnstructin imprvement prject, which may be implemented utilizing federal aid highway funds, in trt litigatin arising frm ccurrences at the lcatins addressed in such dcuments r data. In 2003, the U.S. Supreme Curt upheld the Cnstitutinality f Sectin 409, indicating that it prtects all reprts, surveys, schedules, lists, r data actually cmpiled r cllected fr 152 purpses (emphasis n riginal). Sme States cnsider infrmatin cvered by Sectin 409 as an exemptin t its public disclsure laws, but curts may nt agree with this interpretatin. Page 3 f 25

4 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin RESOURCES Many f the supprting dcuments that dn t have web sites but are used in this class are present at: Examples f crash reprt frms frm arund the cuntry including Michigan s UD 10 frm. Michigan UD 10 Manual & Reprt 10_Manual_2004_91577_7.pdf Michigan Crash Facts: Annual Crash Data Reprt First Editin f the HSM NCHRP prject #17 36 http// Page 4 f 25

5 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Mdule 2 Netwrk Screening Methds NOTES: Netwrk Screening: Screening is smetimes referred t as surveillance. It is used t find high crash areas f the rad netwrk. There are many screening methds available, each with its wn benefits and detractins. Dark Sptting: Visually finding high crash lcatins by pltting them n a map. Psitive Easy t use and understand Simple methd that can be dne quickly with GIS sftware Negative Difficult with large number f crashes Can be subjective, there are n standards that identify what t many crashes lk like Sme clrs grab the eye thers hide Spacing and verlap may cause the same number f crashes may appear wrse based n spacing Zm Level May appear better r wrse at different magnificatins Crash Frequency: Used at intersectins primarily. Crash density is used n segment lcatins. Is actually a crash rate based n time. Crash Frequency = = Yearly crashes Psitive Easy t use and understand Negative Bias fr high vlume intersectins mre traffic = mre crashes Desn t take in t accunt expsure Need t stratify netwrk t accunt fr bias, Example High vlume, med vlume, lw vlume Page 5 f 25

6 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Crash Density: Used n rad segments away frm intersectins. Similar t crash frequency fr intersectins except it takes int accunt the length f the rad segment. Crash density = = Yearly crashes per mile Psitive Easy t use and understand Negative Segmentatin can be an issue, either dividing dense lcatins r having small segments with a few crashes that lk inrdinately bad due t the small segment size Bias fr high vlume lcatin mre traffic = mre crashes Desn t take in t accunt expsure Need t stratify netwrk t accunt fr bias, Example High vlume, med vlume, lw vlume Crash Rate: Can be used fr intersectins r can be used fr rad segments if segment length is accunted fr. Crash Rate Intersectin =,, = Crashes per millin entering vehicles (MEV) Crash Rate Segment =,, = Crashes per mile per millin entering vehicles Psitive Easy t use and understand Accunts fr expsure using traffic vlumes Negative Bias fr lw vlume lcatins with a few crashes Assumes relatins between crashes and vlume are linear, which is generally cnsidered nt true Need full vlume infrmatin t screen netwrk Page 6 f 25

7 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Equivalent Prperty Damage Only Methd: Used fr intersectins. Equates the cst f crashes f different severity t a dllar amunt that the crash csts sciety. EPDO = = Number f EDPO Crashes Mdified EPDO = & = Number f EDPO Crash Psitive Easy t use and understand Takes in accunt severity Negative Bias fr lw vlume lcatins with a small number f sever crashes Des nt accunt fr expsure Weighting Methds: Used fr intersectins. Equates negative r psitive pint scres t specific features f crashes based n cnditins. Creates a unified tally based n the ttal pints. Psitive Can identify very specific details f a crash lcatin Can accunt fr severity Negative N guidance fr assigning weights Des nt accunt fr expsure Page 7 f 25

8 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin RESOURCES: FHWA Reprt n Crash Csts: Crash Cst Estimates by Maximum Plice Reprted Injury Severity Within Selected Crash Gemetries Natinal Safety Cuncil Estimates f Crash Csts SEMCOG Safety Manual Infrmatin n screening methds Paper frm Iwa DOT n crash Methdlgies Page 8 f 25

9 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Classs Ntes, References & Supprting Dcumentatin Mdule 3: Cleaning Up Crash Dataa NOTES: Un lcatable Crash Example: Officer Descriptin: 50 frm the entrance f Wal Mart parking lt n US 28 Since crashes are referenced t an intersectin using the MALI referencing system, adding a lcatin based ff a landmark becmes un lcatable. Un Mappable Crash Example: Sme crashes may n lnger be mappable because the physical lcatin f the crash as recrded is nt pssible. Fr example a gemetric change in the rad may make the crash n lnger mappable because the physical lcatin n lnger exists. Figure 1: When the crash ccurred the lcatin described can be mapped Page 9 f 25

10 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Classs Ntes, References & Supprting Dcumentatin Figure 2 After a gemetric change, the lcatin is n lnger physically pssible t map UD 10 Images: T get UD 10 images frm 2004 thrugh 2007 yu need t create a user accunt. http: // T create a user accunt, g t: Fill ut the frm then call t validate yur accunt. Yu can then enter yur user name and passwrd under the tp menu item Tls then t Optins. See Figure belw. Page 10 f 25

11 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin RESOURCES Michigan UD 10 Manual & Reprt 10_Manual_2004_91577_7.pdf First Editin f the HSM NCHRP prject #17 36 Chapter 4 Netwrk Screening http// Page 11 f 25

12 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Mdule 4: Site Level Cllisin Analysis NOTES: Crash Diagrams: The gal in creating a crash diagram is t uncver any patterns in the data which may pint t causal factrs that can be crrected r mitigated. Crash Data Histry: Typically use 3 r mre years f data fr analysis. T shrt f a perid makes analysis mre subject t anmalus results frm ne time r rare events. T lng f a time may shw results f changes in traffic vlume, r physical changes at the intersectin. Site Visits: Site visits are necessary t give cntext t the data and t give clues t causal factrs. The value f bserving a lcatin first hand can nt be ver stated. Site inspectin check lists are included in Appendix B f NCHRP 457 RESOURCES NCHRP Reprt 457: Evaluating Intersectin Imprvements Site inspectin check list Appendix B First Editin f the HSM NCHRP prject #17 36 Chapter 3 Fundamentals Chapter 5 Diagnsis http// Page 12 f 25

13 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Mdule 5: Site Level Cllisin Analysis NOTES: Gemetric Analysis: This type f analysis lks fr prblems r deficiencies assciated with the gemetric design f the facility. Deficiencies such as pr sight distance, excessively steep rad grade r pr curve radius wuld be likely t be uncvered in this type f a review. The main resurces are the AASHTO Green Bk and MDOT s Lcal Agency Guidelines fr 3R and 4R prjects. Cnditin Diagram This is a basic sketch that may be rughly t scale. An example is shwn in the figure belw. Traffic cntrl / signing / marking Number f lanes Directin f travel Parking lcatin Obstructins Apprach grade Medians r islands Intersectin alignment Figure 3: Example Cnditin Diagram Page 13 f 25

14 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Operatinal Analysis: This analysis is targeted at determining if pr perating cnditins may be leading t traffic crashes. Speed Traffic vlume Delay, density and gap studies Signal timing Human Factrs Analysis: This class f analysis attempts t determine hw the user perceives r reacts t the rad envirnment and lks fr areas that may trick r cnfuse drivers. Generally speaking human factrs relate t the fllwing questins: Visibility: Can yu see it? Expectancy: D yu expect it t be there? Cnsistency: Is it the same at ther lcatins? Visual wrklad: Can yu understand what it is? Aerial Phts: RadSft can imprt SID and SHP files t display alngside the rad netwrk. The Michigan Center fr Gegraphic Infrmatin (CGI) has a rich surce f aerial phts and ther shape files in the Michigan Gegraphic Data Library at: Under the Theme sectin f the library there are digital resurces cvering aerial imagery, census data, gelgy data, grundwater and surface water data, sectin lines, and sil types t name a few. Almst all f this data can be directly imprted int RadSft as a layer. Page 14 f 25

15 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin RESOURCES NCHRP Reprt 457: Evaluating Intersectin Imprvement Site inspectin check list Appendix B Michigan DOT Lcal Agency Guidelines fr 3R and 4R prjects gemetrics_77543_7.pdf AASHTO Green Bk: Gemetric Design f Highways and Streets Fr sale at: bin/detail?prduct_id= NCHRP 336: Rad Safety Audits Transprtatin Research Bard: Highway Capacity Manual Iwa State University: Handbk f Simplified Practices fr Traffic Studies Manual f Transprtatin Engineering Studies NCHRP 600 Human Factrs Guidelines fr Rad Systems, Human Factrs in Traffic Safety, Secnd Editin (bk) by Rbert E., Ph.d. Dewar, Paul L. Olsn Michigan Gegraphy Data Library First Editin f the HSM NCHRP prject #17 36 http// Page 15 f 25

16 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Mdule 6: Selecting Cuntermeasures NOTES: Many factrs influence the ccurrence f crashes. Several research prjects have shwn that crashes usually ccur as a result f several factrs, nt usually just ne factr. Sme factrs that may cause crashes include the fllwing: Driver Vehicle Radway Envirnment Driver Cnditin Reflexes Attentiveness Experience Alchl & drug use Driver aggressiveness Human Factrs Visibility Expectancy Cnsistency Wrklad Vehicle Handling characteristics Maintenance Radway Gemetry Maintenance Surface cnditin Envirnmental Rain / snw / fg Steps in identificatin f deficiencies and selectin f cuntermeasures 1. Detect underlying crash pattern if any 2. Use ther site level analysis t identify factr 3. Determine pssible causal factrs 4. Determine ptential remedies 5. Evaluate ptential crash reductin fr remedies 6. Select mst cst effective remedy Page 16 f 25

17 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin RESOURCES MDOT Time Of Return Spreadsheet NCHRP Synthesis 321: Radway Safety Tls Fr Lcal Agencies SEMCOG Traffic Safety Manual Table 4 5 t 4 10 causes and cuntermeasures NCHRP 500 Series Manuals Guides fr Reducing Cllisins at Specific Lcatins FHWA Desktp Reference Fr Crash Reductin Factrs Minnesta Benefit Cst Analysis Fr Transprtatin Prjects Guide Guidance v2.pdf Page 17 f 25

18 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Michigan DOT Safety Imprvements and Crash Reductin Factrs Prpsed Imprvement Hrizntal Curve Flattening Superelevatin Mdificatin Vertical Curve Mdificatin Cnstruct Center Left-Turn Lane Cnstruct Right-Turn Lane Intersectin Imprvements (Realignment, Sight-Distance Imprvements, Radii Imprvements, Etc.) Install/Upgrade Flashing Traffic Signals Install/Upgrade Pedestrian Signals Install Guardrail Slpe Flattening Widen Shulders t Standard Width Imprve/Upgrade Signing and Pavement Markings at Intersectins Install/Upgrade Signing/Delineatin n Hrizntal Curves Remve Fixed-Objects Frm Clear Zne (Trees, Culverts, Etc.) Install Centerline Rumble Strips Prjected Crash Reductin 30% Reductin: Head-On, Sideswipe, Fixed-Object, Overturn 20% Reductin: Head-On, Sideswipe, Fixed-Object, Overturn 20% Reductin: Head-On, Sideswipe 10% Reductin: Fixed-Object, Overturn 80% Reductin: Rear-End Left-Turn 50% Reductin: Head-On Left-Turn 20% Reductin: Head-On, Angle, Other* 15% Reductin: Nn Left-Turn Rear-End 65% Reductin: Rear-End Right-Turn 20% Reductin: Nn Right-Turn Rear-End, Sideswipe-Same Directin 30% Reductin: Angle 15% Reductin: Rear-End 10% Reductin: Head-On, Sideswipe, Pedestrian, Bicycle, Left-Turn Related 30% Reductin: All Crash Types 30% Reductin: Pedestrian, Bicycle 55% Reductin: Fatalities and A Injuries 15% Reductin: Fixed-Object, Overturn 15% Reductin: All Crash Types 30% Reductin: Angle, Rear-End 10% Reductin: Head-On, Pedestrian 20% Reductin: Head-On, Sideswipe, Fixed-Object, Overturn 75% Reductin: Fixed-Object Crashes 55% Reductin: Sideswipe-Oppsite, Head-On Install Shulder Rumble Strips 25% Reductin: Fixed-Object, Overturn Cnstruct Rundabut 76% Reductin: Fatalities and A Injuries 39% Reductin: Minr & PDO Crashes Cnstruct Sidewalk fr Pedestrians 85% Reductin: Pedestrian Crashes Imprve Access Management 10% Reductin: Angle, Rear-End Prvide All-Way Stp-Cntrl Operatin at Intersectin 60% Reductin: All Crash Types * Other includes any ther crash which might be mitigated by the additin f a center left turn lane in the judgment f the crash analyst. The references listed belw are the surces recgnized by MDOT fr btaining crash reductin factrs. If yu have a situatin that nne f these surces can prvide a crash reductin factr fr, please cntact Jim D Lamater, P.E., MDOT Lcal Agency Prgrams Safety Engineer, at , fr review and apprval t use alternative reference surces. 1). MDOT Safety Prgrams Unit Crash Reductin Factrs (As recmmended by K. Kunde, P.E.); Octber, ). Selectin Prcess fr Lcal Highway Safety Prjects Transprtatin Research Recrd 847; ). UKTRP 85 6, University f Kentucky; March, Page 18 f 25

19 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Mdule 7: Befre and After Studies NOTES: Regressin t the mean: Crashes are psud randm events, meaning that they are hard t predict and have a randm cmpnent t their ccurrence. Because f this, fr a given site the number f crashes will fluctuate up and dwn ver time, but ver the lng run, if things are nt changed, the value will hver arund an average value. When a site is picked fr study slely n the fact it has a high incidence f crashes ver a shrt perid f time, it will be subject t regressin t the mean bias. Regressin T The Mean Bias Average = 31 Figure 4: In 2004 this site had a high incidence f crashes. Even if nthing was dne t change safety, the next year it had 19 fewer crashes. Cnfunding Factrs: Changes in traffic vlume, land use, vehicle r driver ppulatin and even weather can cnfund standard befre and after analysis if nt crrected fr. Page 19 f 25

20 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Direct Reprting f Results: Is an easy methd f getting sme indicatin f the effectiveness f a treatment is direct reprting f results. This methd may nt prvide cnclusive results and ffers n methd fr crrecting fr regressin t the mean r ther cnfunding factrs. Direct reprting shuld nt be the basis f creating crash reductin factrs r high value, plicy guiding studies. It shuld nly be used as a rugh gauge f effectiveness if n ther methds are pssible. Befre After Percent 2001 t t 2006 Change Targeted Crashes Crrectable Crashes % Other Intersectin Crashes % Ttal % Severity Incapacitating Injury & Fatal % Nn Incapacitating Injury % Prperty Damage Only % Rate (Per MEV) Crash Rate % Severe Injury and Fatality Rate % Expsure Netwrk Wide Crashes (Ttal) 17,990 18, % Traffic Lcatin (MEV) % Figure 5: Example f direct reprting f results Page 20 f 25

21 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Test Fr Statistical Significance: Z 1 = Test Statistic f a = # Crashes After f b = # Crashes Befre z 1 = f a f f a + b f b Example: Befre = 15 Crashes After = 12 Crashes z1 = = Cmpare Z scre t standard nrmal table t see the level f significance f change. Page 21 f 25

22 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Standard Nrmal Table Page 22 f 25

23 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Naïve Befre And After Study: This methd uses crash cunts during a perid befre and after t determine a change in safety. Usually 3 years f data fr each perid is used. Fr the study t be cnsidered crrect and valid, the assumptin that n ther factrs have changed during the study perid which include changes in (traffic, weather, vehicle driver behavir, etc) must be made. Typically these assumptins are hard t meet, but in mst case this methd will prvide reasnable results. Naïve Befre and After Calculatins: λ = sum f crashes in after perid K = sum f crashed in befre perid r d = duratin f after perid / duratin f befre π = r d (K ) = estimate f untreated after perid π var = (r d ) 2 (K ) = variance f untreated after perid σ= π λ = Reductin in crashes due t treatment σ var = (π λ) 0.5 = standard deviatin f reductin Index f effectiveness λ π Θ = ( 1+ π 2 π var ) Standard Deviatin f effectiveness Θ var π 1/ λ + 2 = ( π Θ var (1 + π ) 2 π var 2 2 ) Befre and After Study with Cmparisn Grup: This methd is useful fr large grup cmparisns f many sites. The methd uses a cmparisn grup f untreated lcatins which are similar t the lcatins f study as a prxy t measuring the change in safety that develps as a result f cnfunding factrs. The methd gives gd results but will nt crrect fr regressin t the mean. Page 23 f 25

24 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin Emperical Bayes Methd: This methd crrects fr regressin t the mean bias and changes in vlume. It can crrect fr ther factrs that may change during the study as well. Hwever this methd requires significant data and skill as a statistician, and may be difficult t explain and tedius t cmplete. This methd shuld be used fr high value studies where significant cnfidence in the results is required. This methd is beynd the scpe f this class. Page 24 f 25

25 Traffic Safety Analysis Frm Finding The Prblem T Fixing It Class Ntes, References & Supprting Dcumentatin RESOURCES Naïve Befre And After Wrksheet Befre and After With A Cmparisn Grup Wrksheet Ezra Heur s web site Observatinal Befre After Studies in Rad Safety by Dr. Ezra Hauer Instructins n Empirical Bayes methd Befre After Studies Rad Safety/dp/ First Editin f the HSM NCHRP prject #17 36 Chapter 9 Evaluatin f Effectiveness Empirical Bayes Methd Cmparisn Grup Studies http// Page 25 f 25