Identification of Dangerous Highway Locations: Results of Community Health Department Study in Quebec

Transcription

1 78 TRANSPORTATION RESEARCH RECORD 1376 Idntification of Dangrous Highway Locations: Rsults of Community Halth Dpartmnt Study in Qubc BRUCE BROWN, CELINE FARLEY, AND MICHELINE FORGUES Dangrous highway locations on numbrd highways within th trritory of on community halth dpartmnt ar idntifid. Thr sourcs of information ar usd: polic accidnt rports, a systmatic inspction of all numbrd highways, and a community survy of municipalitis, polic, and halth srvic providrs. Th location of all polic-rportd fatal and srious-injury accidnts wr rviwd and corrctd, and corrctions wr submittd to th rporting jurisdiction; this rsultd in a 20 prcnt incras in th numbr of ths rports attributd to numbrd highways. Th initial polic-rportd data includd 11,538 accidnts with and without victims occurring on th 271 km of numbrd highways in th trritory btwn 1984 and A wighting systm basd on th svrity of injury for ach polic-rportd injury was usd in th initial scrning procss; th influnc of diffring wighting schduls using corrctd and uncorrctd location data is prsntd in a matrix. Wightd injury frquncis pr unit distanc and wightd injury rats pr 100 million vhicl-km ar prsntd for all sits and for all numbrd highway sgmnts. Priority sits ar rankd considring injury frquncis and injury rats. Th convrgnc of idntification by polic-rportd data, by highway invntory, and by community rporting is prsntd. Th 28 priority sits rtaind for furthr study covr about 6 prcnt of th numbrd highways in th trritory but account for 53 prcnt of daths, 30 prcnt of srious injuris, and 32 prcnt of minor injuris from accidnts rportd by polic. Community halth dpartmnts (DSCs) in Qubc hav bn working in th fild of highway safty sinc th arly 1980s. At th Sixth Canadian Multidisciplinary Road Safty Confrnc, th dpartmnts in th Montrgi ara of Qubc prsntd an ovrviw of thir work on idntifying dangrous highway locations in thir rgion (1). W now rport th final rsults of this work in gratr dtail for th trritory of on of th four participating dpartmnts. Th idntification and corrction of hazardous highway locations hav rcivd a grat dal of attntion across North Amrica ovr th past 25 yars; it is particularly vidnt in th nginring litrat~r. Rviws of mthodology for this work ar availabl as wll as rcnt rviws of th rlationships btwn spcific highway infrastructur lmnts and th frquncy of roadway-associatd accidnts and th svrity of associatd injuris (2-5). Travl-lan width, shouldr width and surfac condition, sidslop charactristics, and highway gomtry, particularly th prsnc of curvs, hav bn rlatd to injury svrity and frquncy. Administrativ Community Halth Dpartmnt, Charls LMoyn Ho~pital, 25 Taschrau Boulvard, Grnfild Park, Qubc, Canada J4V 208. rgulations rqumng th idntification and corrction of dangrous highway locations in th Unitd Stats hav bn dfind by fdral law sinc Cost-ffctivnss and costbnfit analyss hav bn proposd to guid highway rhabilitation programs with rspct to infrastructur lmnts (6). Mthodologic issus hav rcntly rcivd mor attntion, particularly concrns about th nd to corrct for rgrssion-to-th-man phnomna whn th valuation of intrvntion ffctivnss is don for "dangrous locations" (7). In Qubc during th past 6 yars, mor than 10 studis idntifying dangrous highway locations hav bn publishd by DSCs and univrsity groups. With th xcption of on study on bridg accidnts, w know of non publishd in indxd pr-rviwd journals. Th Ministry of Transport in Qubc has also bn concrnd by this subjct and in 1990 announcd a funding program for th corrction of dangrous highway locations. Inadquacis of th localization mthods usd in polic rports in Qubc hav bn idntifid rpatdly. Th coordinat localization is basd on "mrcators," 1- x 1-km squars dfind by longitud and latitud numbrs; this is th standard computrizd localization mthod usd by polic in Qubc. In 1987 th Ministry of Transport announcd its intntion to introduc a link-nod idntification systm for accidnt localization; this projct has sinc bn transformd into a projct localizing sits using satllit-basd tchnologis. W prsnt th mthodology and rsults of our hazardous highway localization work dvlopd from a public halth prspctiv applid at a local lvl. W viw this mthod as a scrning tool for th prsumptiv idntification of unrcognizd (or at last uncorrctd) dangrous highway locations (8). In much th sam sns as mdical scrning tsts, th "cass" bing idntifid (in this discussion, dangrous highway locations) nd furthr invstigation bfor th initial diagnosis is confirmd or rjctd. As in all scrning tsts, som cass will b idntifid falsly as bing dangrous sits (fals positivs) and som dangrous sits will not b idntifid (fals ngativs). W must mphasiz that a scrning tst is not diagnostic and rprsnts only an initial xamination that must b followd up by mor invstigation. Th valuation of th ability of a scrning tst to discriminat btwn cass and noncass is dpndnt on a "gold standard" that idntifis cass with and without th condition bing studid. Th prvalnc of th condition in th population will influnc th prdictiv valu of th tst in th study population.

2 Brown t al. In addition, th usfulnss of a tst will dpnd on a sris of dfind factors that includ th importanc of th condition (in trms of costs and suffring), th availability of ffctiv tratmnt for idntifid cass, and som knowldg that th arly idntification (bfor th condition bcoms symptomatic) of th condition will bnfit th patint or socity. Th analogis for th cas of dangrous highway locations ar clar, but th absnc of a tru standard against which prsumptiv cass ar judgd rmains a practical problm. W hav dalt with. this by choosing a somwhat arbitrary cutoff point, slcting only th "most xtrm" cass in our population. STUDY AREA Th gographical ara xamind by this study is on th south shor of th St. Lawrnc Rivr nar Montral and covrs an ara of about 100 x 20 km; 438,000 popl liv in th ara. It is part of a largr administrativ trritory, th Montrgi, for which w prsnt polic-rportd motor vhicl mortality data in Tabl 1. In Tabl 1 w compar stimats of rats of dath pr 100 million vhicl-km of travl on our rgion's highways with thos on U.S. highways. Th U.S. data includ 100 prcnt of motor vhicl-rlatd daths occurring in th Unitd Stats as rportd by th Fatal Accidnt Rporting Systm. W would lik to undrlin two points: 1. Th dath rat incrass with dcrasing infrastructur quality for th numbrd highways. 2. Most daths associatd with roadway us occur on numbrd highways. In th cas of th U.S. data, 57 prcnt of daths occur on 22 prcnt of th total roadway distanc. Intrprting Tabl 1 to indicat that highways in th Montrgi ar "wors" than thos in th Unitd Stats bcaus dath rats for ach roadway catgory ar highr in th Montrgi should b don with caution. It should b notd, howvr, that whn ths data wr collctd, rats of sat blt us wr about thr tims highr in Qubc than in th Unitd Stats. If all othr factors wr qual, and if sat blt us dos ffctivly rduc th liklihood of dath, on should xpct lowr dath rats on Montrgi roads. It would b quit simpl and inxpnsiv to us th mthodology prsntd in this papr to dtrmin th quality of highway infrastructur in diffrnt jurisdictions. On th basis of our intrprtation of Tabl 1-using in part th logic attributd to Jss Jams whn askd why h robbd banks ("Bcaus that's whr th mony is")-this study is limitd to th idntification of hazardous highway locations on numbrd highways. Th rst of th papr dals with th data on numbrd highways givn in Tabl 2. Information about th 271 km of numbrd highways was thus xamind. In th 4 yars of rporting, 11,538 accidnts wr rportd on ths highways, of which 2,232 wr accidnts with victims. Ths rprsnt 29 prcnt of all rportd accidnts, 58 prcnt of all daths, and 38 prcnt of all svrly injurd victims in our trritory. METHODOLOGY Th dfinition of hazardous highway locations usd in this study is that proposd by Zgr: "highway spots, intrsctions or sctions with an abnormally high accidnt xprinc (frquncy, svrity or rat) or potntial" (2). Th oprational dfinition includd all of ths lmnts, that is, frquncy, svrity, rat, and potntial for injury. Th first thr lmnts wr drivd from polic accidnt rports and highway traffic flow and distanc data availabl for all highways in our ara (9,10). Tratmnt of ths data is furthr dfind latr in th papr. Th fourth lmnt, accidnt potntial, is drivd from th systmatic visual inspction of th 271 km of numbrd highways using a mthodology basd on a rport by Zgr and furthr dscribd latr in th papr (3). In addition to th accidnt rport and highway invntory mthods, w addrssd a community survy qustionnair to all municipalitis, community clinics, ambulanc srvics, and municipal and provincial polic in our ara. Thy wr askd about thir prcptions of th importanc of dangrous highway locations and th idntification of spcific sits. This mthodology is also furthr dscribd latr. To th bst of our knowldg, this is th only rport of such a combind idntification mthodology. Innovativ fa- 79 TABLE 1 Motor Vhicl-Rlatd Fatality Rats for Unitd Stats (1985) and Montrgi ( ) Highway catgory Total numbr of daths Fatality rat pr 10 1 vh.:.km USA Montr9i USA Montr9i Intrstat ,7 0,9 Principal ,7 2,7 Scondary ,5 3,8 Unnumbrd ,6 N/A Total Sourc: TRB (!) and calculations by community halth dpartmnts from MTQ and Qubc Automobil Insuranc Socity Data (SAAQ).

3 80 TRANSPORTATION RESEARCH RECORD 1376 TABLE 2 Distribution of Motor Vhicl Injury Victims by Svrity of Injury and Catgory of Highway Sit of Injury, Trritory of DSC Charls LMoyn, Highway catgory Highway lngth Numbr of victims (km) Daths Svr Minor injury injury Intrstat (# 0-99) Principal (# ) Scondary (# ) Total (58\) (38\) (26\) Entir trritory Not availabl 175 l Sourc: Qubc Automobil Insuranc Socity, Ministry of Transport of Qubc. turs includ th us of corrctd localization data for all fatal and svr-injury accidnts, th us of a svrity indx including only injury accidnts, and th intgration of ths mthods for slction of priority sits for furthr valuation. Accidnt Rport-Basd Mthodology Data Collction All polic-rportd injury accidnts wr initially xamind using a computrizd data bas. Th location of fatal and svr-injury accidnts (1,359 accidnts, 1,658 victims) wr corrctd for th highway numbr and for th mrcator numbr. As shown in Tabl 3, this rsultd in a 20 prcnt incras in th numbr of rports attributd to numbrd highways (from 438 rports bfor corrction to 526 rports aftr corrction). This is primarily du to th us of highway nams without th corrsponding numbr in som rports, particularly for highway sctions passing through highly urbanizd aras. Th numbr of accidnts occurring on numbrd highways with both highway numbr and mrcator idntifid incrasd by 88 prcnt (from 267 to 503 aftr corrction). Nintn prcnt of all fatal and svr-injury accidnt rports wr corrctd; mrcator numbrs wr corrctd only for rports attributd to numbrd highways. Aftr corrctions, a computr printout of all corrctd rports was submittd to th polic dpartmnt rsponsibl for having compltd th rport. Twnty-on polic dpartmnts wr contactd, and thy confirmd, with fw xcptions, th appropriatnss of our corrctions. Data Tratmnt As a scrning tool dvlopd from a public halth prspctiv, w chos to us injury victims as our unit of analysis.. Most nginring litratur rports us accidnts, somtims stratifid by svrity, as th unit of study. It is our undrstanding that th diffrnc in th two units will b most vidnt in th cas of svr frontal collisions; our mthod will in gnral attribut gratr importanc to ths collisions bcaus, for a givn accidnt svrity, th frontal collision will gnrat mor victims than, for xampl, a singl-vhicl fixd-objct collision of quivalnt accidnt svrity. In ffct, a singl svr-injury accidnt that gnrats thr svrly injurd victims will b countd thr tims in our systm but only onc in a classic nginring study. An injury svrity indx that prmittd th us of a singl numric valu to xprss th total cost of all injuris associatd with a particular location was applid. Th valus chosn wr rlatd to th dirct and indirct conomic costs of injuris as dtrmind by th Qubc Automobil Insuranc Socity (11). Fatal injuris wr rlativly undrvalud in this. systm rlativ to Qubc conomic cost data and costs basd on othr mthodologis (11-14). Th valus attributd for diffrnt injury svrity ar as follows: TABLE 3 Corrctions Mad to Accidnt Rports for Fatal and Svr-Injury Accidnts, Trritory of DSC Charls LMoyn, Highway numbr prsnt Mrcator numbr Prsnt Absnt Highway numbr absnt Mrcator numbr Prsnt Absnt Total Bfor corrction Aftr corrction l 359

4 Brown t al. Fatal injury-100 Svr injury-20 Minor injury-3 Th wightd injury frquncy for a particular location is calculatd as th sum of th numbr of victims of a givn svrity (Ni) multiplid by th corrsponding svrity (Si), rpatd for ach svrity lvl: wightd frquncy 3 L Ni Si (1) i=l Th wightd frquncy for highway sctions (from 12 to 47 km long) for ach of th 12 numbrd highways in our trritory wr also calculatd as wightd frquncis pr kilomtr of roadway. Wightd injury frquncis wr calculatd for ach of th mrcators through which numbrd highways passd. W xamind th influnc of using corrctd and uncorrctd highway location data as wll as th significanc of th choic of svrity indx. This was don by comparing th 50 highst wightd frquncy mrcators that would b slctd by using ach of four diffrnt wighting schms and comparing bfor-corrction data with aftr-corrction data. Ths comparisons ar prsntd as a corrlation matrix in Tabl 4. Th corrction of location data alon rsultd in a minimum of 9 (18 prcnt) and a maximum of 22 (44 prcnt) of th 50 mrcators' changing. In our complt rport w hav also shown that btwn 10 and 34 prcnt of th 50 highstfrquncy mrcators chang solly on th basis of th us of diffrnt wightd injury frquncy SGals (i.., diffrnt svrity indxs) (15). Th procss of idntifying individual hazardous sits using accidnt rports was don in two stags. Th first stag involvd slcting mrcators with both high wightd injury rats and frquncis. In th scond stag, data for ths mrcators wr xamind to idntify spcific sits (.g., intrsctions) within th mrcator, and ths wr rtaind as th sits for study. Victims from accidnts occurring at th sits wr idntifid and svrity scors calculatd. An intrsction gnrally includd 200 on ach approach as attributd to th intrsction. Wightd injury rats for th 100 highst-valu wightd frquncy mrcators wr calculatd by dividing th wightd injury frquncis by th vhicl-kilomtrs of travl for th 4 yars of xposur. An stimat of 1.0 km as th lngth of numbrd highway in ach mrcator was usd for this calculation. Traffic volum stimats wr thos for 1986 applid to ach of th 4 yars: ths wr supplid by th Ministry of Transport of Qubc. Wightd rats ar xprssd as wightd frquncis pr 100 million vhicl-km of travl. Figur 1 prsnts th rsults of th first stag in this slction procss. Wightd rats and frquncis ar plottd for th 100 mrcators with th highst-wightd frquncis. This modl of prsntation is basd on th work by Barbarsso in (16). Th considration of injury rats and injury frquncis rprsnts diffrnt and gnrally opposing prspctivs for th idntification of dangrous sits. Rats rflct a masur of risk for th individual roadway usr for a givn road; frquncis rflct th ovrall accumulatd socital (collctiv) cost of injuris for a particular sit. Rational invstmnt of limitd rsourcs for maximal socital bnfit will prioritiz th xamination of sits with high injury frquncis, all othr lmnts bing qual; howvr, considrations of quity and risk rduction for individual usrs rquir attntion to limit disparitis in rats. As sn in Figur 1, vn though only th 100 highst-frquncy mrcators ar includd in th figur, high-frquncy mrcators ar usually thos with gratr traffic volums (i.., Intrstats and Routs 100 to 199) whras high rat mrcators ar thos with lss traffic (Routs 200 to 400). Using xplicit critria for both rats and frquncis, w idntifid 56 mrcators in thr priority groups for furthr study (Tabl 5). A fourth group of 44 mrcators with wightd frquncis of lss than 250 and wightd rats of lss than 1,000 pr 100 million vhicl-km wr liminatd from furthr study. Th scond stag of idntification of spcific sits within mrcators was don by xamining printouts of locations for injury accidnts within ach of th 56 mrcators rtaind for study. It was possibl to idntify spcific intrsctions for many of ths mrcators, but in othr cass this was not radily apparnt. For thos, th ntir mrcator was rtaind and idntifid as a dangrous sction at this stag of analysis. 81 TABLE 4 Concordanc of 50 Highst-Frquncy Mrcators Dtrmind Using Four Injury Svrity Indxs and Bfor- and Aftr-Corrction Accidnt Location Data Svrity indx Indx l Indx 2 Indx 3 Indx 4 (10-9-3) (10-9-0) ( ) ( ) Svrity indx Svrity indx Svrity indx Svrity indx Numbrs shown ar th numbr of concordant pairs for th 50 highst frquncy mrcators compard 2 at a tim. Numbrs in parnthss rfr to th indx for (fatal - svr injury - minor injury) victims.

5 = I 82 TRANSPORTATION RESEARCH RECORD 1376 w i 10 ~ t 8 d n j u r 4 y 2"f i t t t ~ ~ - - ; 1.3~-18 i b..-- l 1:04-6 ~ R ~ ~32-1l ~ ;._ ~ a t :-' (.. ~- =.:L.. :.!.\ f&.~! ~ ~ ~ '--_._...sc:=--~.. --=-_._~~-'-~_..~~-'--.:..:..._i~~._~.~~_j Wightd Injury Frquncy FIGURE 1 Wightd injury rats and frquncis for th 100 highstwightd injury frquncis for mrcators on numbrd highways, trritory of DSC Charls LMoyn, (1). TABLE 5 Numbr of Mrcators Rtaind for Furthr Study Idntifid According to Priority Group Group Numbr of mrcators cods rtaind Dfinition Priority l. Priority 2 Priority (1) X > 500; or (2) Y > 3 000; or (3) 350 < X < 500 and < Y < (l) 350 < X < 500 and Y < 2 000; or (2) X < 350 and < Y < 3 000; or (3) 250 < X < 350 and < Y < (l) 250 < X < 350 and Y < l 000; or (2) X < 250 and l 000 < Y < X = wightd injury frquncy Y = wightd injury rat Highway Safty-Hazard Invntory Zgr t al. rviwd mthods for th idntification of hazardous highway lmnts (3). Principally on th basis of th modl usd by th Oakland County (Michigan) Road Commission prsntd by Zgr t al., w dvlopd a data collction form for th valuation of th following roadway lmnts: fixd objcts, guardrails, roadway gomtry, signalization, and roadsid charactristics othr than fixd objcts. A hazard rating for fixd objcts and th othr charactristics, such as distanc from th dg of th road, was dfind on th basis of th Oakland study (15). Each lmnt was assignd a numric svrity rating basd on location and rigidity of th obstacls; ratings rangd from 3.0 to 9.3 and wr rducd to thr diffrnt catgoris: A-most hazardous with scors 7.5 to 9.3, B-intrmdiat lvl, and C-last hazardous, with scors of 3.0 to 4.8. All 271 km of rout wr travld and scord in both dirctions by two obsrvrs, on of whom did th sam scoring for two othr DSC trritoris. Idntifid highway hazards wr photographd and a running commntary was taprcordd to aid compltion of th writtn obsrvation coding sht. Each hazardous lmnt idntifid was codd into Catgoris A, B, or C. A rport of hazardous lmnts for ach numbrd highway was prpard. Forty-fiv A-ratd sits wr idntifid using this mthod. Community Survy A community survy was maild to th 21 local municipalitis as wll as to community clinics and rgional administrations in Of th 29 rspondnts, 90 prcnt thought that th idntification and corrction of dangrous highway locations was important or vry important. Rspondnts idntifid 83 sits that thy considrd dangrous or potntially dangrous; 38 of ths sits wr on numbrd highways.

6 Brown t al. 83 accidnt rports (priority I, II & I n 51 ommunity survy n 38 PR+ HI 7 22 \ ay invntory n 45 PR+ CS 12 +HI +CS 6 FIGURE 2 Mthod of idntification of 95 potntially dangrous highway locations according to information sourc: Priority 1, 2, and 3 mrcators idntifid from accidnt rports, th community survy, or th highway safty-hazard invntory. TABLE 6 Critria for Slcting Priority Sits Critria All sits idntifid within priority 1 mrcators (tabl 5) All sits idntifid within priority 2 mrcators (tabl 5) for whi~h on or th othr of th following critria apply: thy hav a highway invntory hazard cod of A, or; thy wr idntifid in th community survy All sits idntifid within priority 3 mrcators (tabl 5) for which both of th following critria apply: thy hav a highway invntory hazard cod of A, and; thy wr idntifid in th community survy Intgration Mthod for Slcting Priority Sits Numbr of sits Ovrall, th thr mthods id'ntifid 95 diffrnt sits on numbrd highways. Figur 2 prsnts ths sits according to th mthod by which thy wr idntifid. Most of th sits wr idntifid by only on mthod; 32 sits (34 prcnt) wr idntifid by two or thr mthods. Th critria in Tabl 6 wr applid to slct th final 28 sits rtaind as priority sits. It should b strssd that all of th final sits idntifid as high priority wr slctd from th 56 mrcators dfind in Tabl 5..RESULTS Th valuation rtaind 28 sits as high priority for furthr study. Thr sits wr on intrstats, 22 wr on principal highways (numbrd highways 100 to 199), and 3 wr on scondary highways (numbrd highways 200 to 399). Th total combind lngth of th 28 sits is 17.6 km, or 6.3 prcnt of th 271 km of numbrd highways studid. Fifty-four daths, PR HI CS Polic rports (priority I, II or III). Highway invntory. Community survy. FIGURE 3 Distribution of 28 sits by mthod of idntification, trritory of DSC Charls LMoyn. 169 svr injuris, and 1,084 minor injuris wr attributd to ths sits; ths rprsnt 53 prcnt of total daths, 30 prcnt of svr injuris, and 32 prcnt of minor injuris attributd to th 271 km of numbrd highways studid. Th mthods of idntification of th 28 sits ar prsntd in Figur 3. Six sits wr idntifid by all thr mthods. Svntn sits ar in rural locations, and 11 ar in urban aras. All thr intrstat sits ar at intrchangs, and fiv of th sits on othr numbrd highways ar at intrsctions. Eightn othr sits ar dfind as highway sctions lss than or qual to 1 km long and may includ svral intrsctions. Th wightd rats and frquncis of injuris for ach of th 12 numbrd highways includd in th study ar prsntd in Figur 4. Th hazardous faturs and injury xprinc attributd to ach of ths sctions is prsntd in our final rport. Frquntly idntifid hazards includ poorly maintaind and poorly alignd guardrails, usually not in continuity with bridg abutmnts; poorly maintaind highway shouldrs; and dficincis in highway gomtry for som highways (particularly Rout 104). Additional faturs ar prsntd in our rgional rport (17). DISCUSSION OF RESULTS This study prsnts svral faturs that w think dsrv furthr attntion. W ar disturbd by th 20 prcnt incras in th numbr of fatal and svr-injury accidnt rports attributd to numbrd highways aftr localization information was corrctd. Small numbrs of rports ar involvd, and on numbrd rout in an urban ara contributd an important fraction of th total; nonthlss, in futur us of polic rports, particularly in aras in which numbrd highways pass through largr urban aras, th undridntification of th importanc of injury accidnts occurring on numbrd highways may rprsnt a significant data tratmnt issu. Th dficincis of th mrcator systm usd in Qubc to localiz accidnts hav bn confirmd in this study; th numbr of fatal and svr injury accidnts with mrcators idn-

7 84 TRANSPORTATION RESEARCH RECORD 1376 w i g h t d 1!04 n j u r 1500t------~---+-~'~' 0 u'dt..-~~-+-~~--... ~.= = = = = = = = -= = ~ ==========I 1000t---._-'-==--==+=~'"'-"-'==~'*"'-~1=1=2~====F=====~=-+=-========~ 1 y R 500 ~~ _ 4--'-'"'-'"--'" a t o..._~~~~-+-~~~~~~~~~~~.._~~~~-'-~~~~~~ Wightd Injury Frquncy FIGURE 4 Wightd injury svrity rats and frquncis for numbrd highways, trritory of DSC Charls LMoyn (Sourc: Qubc Automobil Insuranc Socity and Ministry of Transport of Qubc). tifid on numbrd highways was incrasd by 88 prcnt aftr our corrction procdur. It should, howvr, b notd that our corrction procdur was simpl and inxpnsiv. Computr printouts of writtn location information ar availabl for all rports, and w basically corrctd th 1,300 rports in 2 days, aftr which printouts wr snt to participating municipal and provincial polic in our ara. Th procss of working with polic was positiv. Thus, dspit data inadquacis, corrctions at a local lvl ar gnrally quit straightforward at this lvl of prcision. W bliv that our us of injury victims as th unit of analysis is innovativ and has som advantags in accidnt svrity counting, whn viwing traffic safty from a public halth prspctiv in th contxt of a scrning study. Ths wr discussd arlir. On disadvantag is th possibility of idntifying fals positivs; for xampl, a singl fatal accidnt involving six daths would gt undu attntion. Th us of both frquncis and rats of injury is, w bliv, a positiv aspct of this study. Th dcision-making procss usd to stablish priority groups was largly intuitiv, howvr, and a mor statistically sophisticatd stratification dcision analysis would b usful. Our highway invntory mthodology is quit straightforward and fasibl for local highway analysis. W prciv th lvl of prcision of our masurmnts to b low, although appropriat as a scrning tool. W hav had no valuation of introbsrvr rliability nor of th validity of our masurmnts. Our dcision to limit th numbr of sits for furthr study to 28 was dfind by our prcption that a largr numbr would ovrload th capacity of local agncis to study th sits. This corrsponds to th rcommndation of th panl rviwing highway accidnt analysis systms; according to this rport 1 man-yar was rquird to analyz and rviw 170 sits for th California Dpartmnt of Transportation in 1978 (2). Ovrall, w think that th approach w hav chosn is a usful pilot projct that contributs to our ability to idntify dangrous highway locations systmatically. Work on this projct was don ovr 4 yars and involvd four halth dpartmnts without xtrnal funding. Th total cost for th dvlopmnt and application of th mthod for th ntir rgion (Montrgi) was lss than $150,000 (Canadian), or about $9,000/yar pr halth dpartmnt; about on-third of costs wr for dvlopmnt of th mthodology, including th initial xprimntation in on subrgion of th Montrgi (17). Th total contribution including dvlopmnt costs for th trritory covrd in this papr (DSC Charls LMoyn) was about $32,000 (Canadian). Sinc spring 1990 w hav bn working with th Ministry of Transport of Qubc, th Ministry of Municipal Affairs, local municipalitis, municipal and provincial polic, and lctd municipal councillors in a pilot projct studying all accidnt rports, including all matrial-damag rports, for th priod as wll as rmdiabl factors rlatd to vhicls, human factors, and th roadway for ight sits across th Montrgi. Th modl usd is basd loosly on th Local Highway Improvmnt Program of FHW A with additional attntion to human and vhicular factors contributing to injury frquncy and svrity (18). ACKNOWLEDGMENTS Th authors wish to thank Pirr Lainss, Aim Lbau, Graldin Qusnl, and Dian Srgri for thir contributions at th rgional lvl that guidd this work. Suzann Rgimbald has patintly and comptntly supportd th authors with hr scrtarial srvics.

8 Brown t al. REFERENCES 1. D. Srgri and B. Brown. Synths d la dmarch d'idntification t d priorisation ds sits dangrux sur ls routs numrots n Montrgi, (in Frnch). Proc., 6th Canadian Multidisciplinary Road Safty Confrnc, 1989, pp C. Zgr. NCHRP Synthsis of Highway Practic 91: Highway Accidnt Analysis Systms. TRB, National Rsarch Council Washington, D.C., ' 3. C. Zgr. NCHRP Synthsis of Highway Practic 128: Mthods for Idntifying Hazardous Highway Elmnts. TRB, National Rsarch Council, Washington, D.C., Spcial Rport 214: Dsigning Safr Roads: Practics for Rsurfacing, Rstoration, and Rhabilitation. TRB, National Rsarch Council, Washington, D.C., C. Zgr t al. Safty Effcts of Cross-Sction Dsign for Two Lan Roads, Vol. 1. Rport FHWA-RD-87/008. FHWA, U.S. Dpartmnt of Transportation. 6. B. Campbll and T. F. Humphry. NCHRP Synthsis of Highway Practic 142: Mthods of Cost-Effctivnss Analysis for Highway Projcts. TRB, National Rsarch Council, Washington, D.C., B. N. Prsaud. Blackspot Idntification and Tratmnt Evaluation. TDS Ontario Ministry of Transport, Downsviw, Canada, A Dictionary of Epidmiology (J. M. Last, d.). Oxford Univrsity Prss, Ministry of Transport of Qubc. Distancs routirs dition 1986 (in Frnch). Qubc Publications, Canada, 1987.' 10. Diagramm d'coulmnt d la circulation sur /s routs du Qu- b (in Frnch). Ministry of Transport of Qubc, Canada ' 11. B. Bordlau. Evaluation ds couts d l'inscurit routir au Qubc, rapport d rchrch (in Frnch). Qubc Automobil Insuranc Socity, Canada, J. J. Lawson. Th Valuation of Transport Safty. Transport Canada, D. P. Ric, E. J. Macknzi, t al. Cost of Injury in th Unitd Stats: A Rport to Congrss. Institut of Halth and Aging, San Francisco, Calif., B. Brown. L'valuation d la valur d la vi humain appliqu n planification d la scurit routir (sits dangrux) (in Frnch). Prsntd at th Confrnc on Highway Safty, Univrsity of Montral, Canada, B. Brown, C. Farly, and M. Forgus. Etud d localisation t d priorisation ds sits dangrux sur /s routs du trritoir du Dpartmnt d sant communautair d l'hopital Charls L Moyn (in Frnch) J. C. Barbarsso t al. Slction Procss for Local Highway Safty Projcts. In Transportation Rsarch Rcord 847, TRB, National Rsarch Council, Washington, D.C., 1981, pp D. Srgri, B. Brown, G. Qusnl, and M. Forgus. Projt d'idntification t d priorisation ds sits dangrux du rsau routir n Montrgi-M thodologi t synths, Vol. 1 (in Frnch) National Highway Institut. Local Highway Safty Improvmnt Program: Usrs' Guid. U.S. Dpartmnt of Transportation, Publication of this papr sponsord by Committ on Traffic Rcords and Accidnt Analysis. 85