Validation of Signalized Intersection Survey Method

Transcription

1 41 Figre 5. Sample otpt of 5-min smmaries and overall smmary for data location. ************** PLA'COS/LFADER *** *VEHCLE CCXJNTS****** *PCU PER HOUR* ** SPEED** **** ***PERCENTLE SPEEOO""**** DTE TME W/S DT CA TR RE or CAR TR RE or MA OPP DT MA OPP DT AVG H D l e 19 4 l D e 29 l D l ) D l 28 3 l D e l D e \'l OD l 11 3 l D l 1 e 24 2 l D **** Sll-!MARY OF XATO 7 E l VEHCLE CClJN'S-PERCENT EAOO-PERCENT OOWMES 5-MN PERCC6 132 CMS DT PLATOOS 2148 TROCl<S RECS OOER MAN OPPOS TOrAL sring speed and obtaining detailed traffic conts for both directions dring periods of lo-traffic demand makes the radar-platoon techniqe a very efficient data-collection method. A 5-min conting cycle length as selected for the Ontario stdy becase it is long enogh for statistical aggregation hile it remains short enogh to reflect any short-term flctation. REFERENCES 1. M. van Aerde and S. Yagar. comparing Manal and Atomatic Techniqes for Recording and Processing Traffic Data. Proc., Organiation for Economic Cooperation and Development Symposim on the Effects of Speed Limits on Traffic Accidents and Transport Energy se, blin, reland, Oct. 1981, 13 pp. 2. s. Yagar and M. van Aerde. Field Stdies on To-Lane Highays: Volme/Capacity Relationships. Univ. of Waterloo, aterloo, Ontario, Canada, Feb. 1981, 266 pp. Pblication of this paper sponsored by Committee on Methodology for Evalating Highay mprovements. Validation of Signalied ntersection Srvey Method A.J. RCHARDSON AND N.R. GRAHAM The development and validation of a manal srvey method for the measrement of performance at signalied intersections are described. The method is easy to se in the field and simply reqires that qee lengths and flos be measred at particlar times ithin each cycle of the traffic signals on each approach being srveyed. The otpt of the program incldes freqency distribtions and smmary statistics for measres of approach delay, stopped delay, stationary qee length, and varios definitions of vehiclar stops. The validation of the srvey method as performed by comparison of srvey measrements ith measres obtained from a videotape recording of intersection operation. The comparison as performed in to stages. First, reslts obtained from the field method ere compared ith reslts obtained by vieing a videotape of the same traffic stream end extracting the srvey data from the videotape. This comparison identified the field observer error in the srvey method. Second, the reslts obtained by sing the srvey method ith the videotape ere compared ith detailed path-trace information obtained from the same videotape. This comparison identified the theoretical error in the analysis calclations associated ith the srvey method. The comparison shos that the field srvey method prodced negligible observer error hile the theoretical error in the srvey method as qite small and ell ithin the bonds dictated by practical traffic engineering reqirements. t is conclded that the srvey method is a simple, yet accrate, ay of determining signalied intersection performance levels. The evalation of signalied intersection performance has long been an isse of concern, a concern that has intensified in recent years ith the changing emphasis in rban transportation planning. Tightening bdgetary constraints have led to redced capital expenditre on transportation and have been partly responsible for the present emphasis on transportation system management. Moreover, there has been an increasing need to acqire more knoledge of demand so that the management of it is both pblicly acceptable and consistent ith an efficient allocation of resorces, both privately and socially. To this end, energy conservation, environmental conseqences, and eqity (in terms of resorce allocation, e.g., time savings) have become important concerns. The measrement of intersection performance, for example, shold no longer be concerned solely ith the motorist bt ith societal goals as a hole and ith the eqitable allocation of resorces to individal members of society. Determination of the level of performance of a signalied intersection has application in traffic engineering planning and design, in the stdy of the effects of physical and operational improvements,

2 42 Figre 1. Original field srvey form. NTERSECTON APPROACH QUEUE LE NG TH DELAY SURVEY START OF GREEN LAST TME VEHCLE QUEUE H M S LENGlll H M s A B C Figre 2. Revised field srvey form. NTERSECTON.. - APPROACH OBSERVER START OF RED DATE TME QUEUE H M S LENGTH QUEUE LENGTH DELAY SURVEY D OBSERVER E DATE / / - START OF GREEN LAST VEHCLE START OF RED TME QUEUE TME FLOW TME QUEUE '--- LENGTH H S AFTER s LENGTH H M S M H M A l B C F D E and in economic analyses. n particlar, analyses of traffic-signal-control strategies, air and noise polltion related to vehiclar traffic, road-ser costs, evalation of bs-priority schemes, effects of different objective fnctions for traffic-signal timing, and capacity and level-of-service calclations all reqire estimates of vehiclar delay, stops, or other measres of performance. The search for a measre of level of performance at an intersection takes its roots at the birth of the traffic engineering profession. An early ork by Greenshields (!) sed a 16-mm camera to captre traffic flo for sbseqent analysis in the laboratory. Since then, a nmber of researchers (-!!_) have contined the search for measres of performance. Reilly and others (!!_) have noted that in the evoltion of performance-measrement techniqes there have been to major problems. First, the definition of the performance-level criteria and second, the techniqe for obtaining sch a measrement. Unfortnately, mch of the previosly reported ork has not clearly defined either the phenomenon to be measred or the details of the measrement techniqes. To overcome many of the deficiencies of previos techniqes, a ne srvey method as developed to assist in the evalation of bs-priority signals () Th is method has previosly been described by Richardson (1). Partly as a reslt of comments by Reilly (11), it as decided that this srvey method shold.;;- sbjected to a comprehensive validation stdy here srvey method reslts old be compared ith reslts obtained from a videotaped recording of intersection operation. The prpose of this paper is to smmarie the reslts of this validation stdy, hich as sponsored by the Astralian Road Research Board. This paper ill only highlight the major points of the stdy7 more complete details of the stdy may be fond in a separate series of reports (12-17). SURVEY METHOD DESCRPTON Before describing the validation stdy, it is necessary to provide details of the intersection srvey method that is the sbject of the validation stdy. The method has been initially described by Richardson (1). Since that time, hoever, the method has been -;;:;bstantially revised and improved, sch that the present analysis program bears little resemblance to the one described earlier. A more p-todate description of the theoretical backgrond to the analysis procedre may be fond in Richardson (14). -The srvey method may be described in terms of three components: inpt, otpt, and special featres of the analysis. The method offers to options ith respect to the inpt data to be collected. The original version of the method, as described in Richardson (1), reqires for items of data to be collected in -;;;y one cycle of the traffic signals on each intersection approach being srveyed. An example of the srvey form sed in the field is shon in Figre 1. At the start of the green phase, the time is recorded in colmn A and the nmber of vehicles stopped in the qee is recorded in colmn B. A mental note is made of the last vehicle in the qee at the start of the green and, hen the qee moves off, the progress of this vehicle is noted. f this end-of-qee vehicle crosses the stop line before the signal changes back to red, then the time at hich it crosses the stop line is recorded in colmn c. The time at hich the signal changes back to red is then recorded in colmn D (colmn E, in this case, is left blank). f the end-of-qee vehicle does not cross the stop line before the lights change back to red, the time at hich the lights change to red is recorded in colmn D and the nmber of vehicles in front of and inclding this vehicle hen the ne qee forms is recorded in colmn E ( colmn C, in this case, is left blank). This process is repeated for every cycle in the srvey period. A limitation inherent in sing the srvey method ith only these data is that it mst be assmed that the arrival rate that as observed dring the red period in each cycle contines throgh the folloing green period. Similarly, the move-off rate observed for vehicles p ntil the last vehicle in the qee at the start of the green is assmed to contine for all vehicles that depart in the crrent cycle. As noted by Reilly (11), both these assmptions may be invalid nder certain circmstances (e.g., coordinated signals or flared intersection approaches). TO enable the srvey method to be sed in sch sitations, a modification as made to the data-collection procedre that, hile slightly increasing the orkload in the field, allos for different arrival rates dring the red and green phases and for changing move-off rates dring the green phase. The modified field srvey form is shon in Figre 2. The procedre is identical to that described above ith respect to Figre l except that after the last vehicle in the qee at the start of the green has crossed the stop line, the observer conts the nmber of vehicles that then cross the stop line before the signals trn red and records this flo in colmn F. f the end-of-qee vehicles does not cross the stop line before the signals trn red, then colmns C and Fare left blank and colmn Eis completed as before.

3 43 Given these relatively meager inpt reqirements, the srvey method prodces a very comprehensive range of otpt statistics. Specifically, it prodces freqency distribtions and smmary statistics (mean and standard deviation) for the folloing performance measres: approach delay, stopped delay, nmber of complete stops, nmber of effective stops (for se in fel-consmption calclations), and maximm stationary qee length in the cycle. The total flo across the stop line and a complete record of signal phasing and timing are also obtained from the analysis program. n calclating these otpt statistics, the analysis program (QDELAY) makes se of a nmber of special featres that have hitherto not been incorporated in intersection srvey method calclations. The analysis program is based on the constrction of trajectory diagrams for vehicles that pass throgh the intersection. n calclating approach delay, se is made of the finding of Allsop (18) that, by considering vehicles ith infinite acceleration and deceleration rates, the approach delay is eqal to the length of the horiontal sections of the trajectories. The QDELAY program, hoever, extends this concept to inclde approach delay that is incrred after the vehicle crosses the stop line (i.e., hile the vehicle is accelerating back p to crise speed). This extension overcomes a problem that is evident in most, if not all, previos srvey methods here approach delay is confined to being pstream of the stop line. Sch a restriction may be most significant in sitations here the average qee length is short, ith a sbstantial amont of approach delay being incrred donstream of the stop line. n calclating stopped delay, the time spent in deceleration and acceleration manevers is sbtracted from the approach delay for each vehicle to reveal the time spent stopped. n many cases, the stopped delay may be ero hen the vehicle does incr approach delay. The rates of acceleration and deceleration sed in this calclation are ser specified and may be chosen to sit the particlar site in qestion. The calclation of vehiclar stops allos for to basic options. First, it is possible to calclate conventional measres of vehiclar stops, sch as the average nmber of complete stops per vehicle or the proportion of vehicles that are stopped. Second, becase the nmber of vehiclar stops is often sed to calclate fel consmption, it is possible to calclate a more appropriate measre of vehiclar stops (termed effective stops) that allos for the effects of partial stops (that is, vehicles that slo don bt do not completely stop) and qee-shffling stops (here vehicles in satrated traffic conditions stop and "shffle" forard several times before clearing the intersection). From the above discssion, it is obvios that the srvey method can be sed in satrated, as ell as nsatrated, traffic conditions. One final point that concerns the srvey method is that, as described in Richardson (1), it can be sed on approaches ith more than one ne by defining a representative end-of-qee vehicle. The only restriction in sing the method in this ay is that flo characteristics (in particlar, the move-off rate) sho ld be similar in each lane. VALDATON OF STUDY DESGN The objectives of the validation stdy ere to identify both the theoretical and observational errors in the srvey method. To this end, the validation stdy incorporated three distinct data-collection phases: l. Field observers sed the srvey method to measre intersection performance. 2, Concrrently, intersection operation as recorded on videotape. Later, observers vieed the videotapes in a laboratory and sed the same srvey method to record the level of intersection performance. J. By sing the same videotaped recording of intersection operation, independent measres of intersection performance ere obtained, to a high level of precision, by tracing the individal movements of a sample of vehicles throgh the intersection. By comparing the reslts of phases land 2, the observational error cold be ascertained. A compar i son ith the reslts from phases 2 and 3 old reveal the theoretical error in the srvey method calclations. The main difficlty in the srvey design as to find stdy site locations, given a rather formidable list of constraints in camera location, traffic flo conditions, general site characteristics, and time and bdget constraints. To isolated, signalied intersection sites ere finally chosen (Nicholson Street and Beaconsfield Parade). Both sites are located approximately 3 km from the Melborne central bsiness district (CBD). The sites ere chosen to give a ide variety of traffic conditions, inclding both peak and off-peak periods. At the Nicholson Street site, a total of 15 h of data as collected, comprising 4 h in the morning peak, 4 h in the evening peak, and 7 h dring the afternoon off-peak. At the Beaconsfield Parade site, a total of 4 h of data as collected, all in the morning peak period. At the Nicholson Street site, here there ere to approach lanes, data ere collected separately for each lane. At the Beaconsfield Parade site, here there ere three throgh lanes, data ere collected for both separate and mltiple-lane sitations. By alloing for different combinations of the times of the srveys and the lane configration, a total of 5 data sets as obtained for comparison. The collection of data by sing the srvey method in the field as relatively straightforard by sing the techniqes described earlier in this paper [and in Richardson (15)). When sing the srvey method in the laboratory, observers made fll se of the stop-frame action of the videotape playback in order to make observations ith great accracy (e.g., to cont the nmber of vehicles in a long qee). n sing the path-trace method, a nmber of factors needed to be acconted for. The definition of an approach-delay section as an essential prereqisite to the collection of path-trace data. The pstream end of the section as defined to be an easily identified point some 1-m pstream from the longest expected qee. The donstream end as defined to be the stop line at the intersection. This as necessary in order to ensre that the video-camera as close enogh to the intersection to obtain a reasonable vie of the stationary qee. The definition of the approach-delay section in this ay, hoever, reqired that the ability of the QDELAY program to calclate approach delay incrred after the stop line be neglected for the validation stdy comparisons. n sing the path-trace method, it is necessary to make an assmption abot the free speed of vehicles throgh the approach-delay section in order to calclate the delay in this section. The free speed as calclated in to ays. First, the speeds of vehicles that passed throgh the section nimpeded ere obtained from the path-trace records, and the free speed as set eqal to the 85th percentile point of the distribtion of nimpeded

4 44 speeds for that approach and time of day. Second, as part of a stdy to determine deceleration rates at the intersections, an estimate as obtained of the speed at hich all vehicles, hether impeded or not, approached the intersection. Both methods gave very similar reslts at both Nicholson Street and Beaconsfield Parade. Extraneos vehicles (that is, vehicles that do not cross both the pstream and donstream ends of the approach-delay section) ere eliminated from all path-trace calclations becase of the difficlties of defining delays for sch vehicles. At each site, extraneos vehicle activity as approximately 2 percent of the total flo across the stop line, Since many delay measrements ere made on a laneby-lane basis, it as necessary to allocate each vehicle in the path-trace srvey to a particlar lane. As ith Reilly and others (8), vehicles ere allocated to the lane in hich they-crossed the stop line. Althogh it is acknoledged that the pathti:ace method does not give completely accrate reslts, it as considered that sch reslts ere as close to the tre sitation as cold be obtained ithin reasonable bdgetary limits. Spport for this contention may also be fond in Reilly and Figre 3. Comparison of srvey reslts hen sed in field and in laboratory. :; 6 oo "' o :::::E?i 4 Q :r :r,- ". o."' <( 2 :::> " "Q :: "'"' so o DATA PONT, BEACONFELD PDE DATA PONT ' NCHOLSON STREET -- 9"/o CONFDENCE LMTS FOR MEAN o-l'"---,----,----,---,----,---,-----, AVERAGE APPROACH DELAY-SECONDS (LAB MODEL) Table 1. Regression of path-trace reslts against measres obtained from se of srvey method in laboratory. Regression Coefficients Correlation Coefficients Variable ntercept a Slope b rb r2 E Approach delays Total -456 ± ± Avg ± ± SD -.45 ± ± Stopped delays Total 43.3 ± ± Avg a.so± ± SD -. ± ± Nmber of stops Total 9. ± ± Avg.1±.4.92 ± SD.18 ±.1.56 ± Nmber stopped Total -. ± ± Proportion.13±.4.88 ± Vehiclar volme-. ±..OD± OD total :cocf'fltient ± 95 percent confidanco ln\crval tor c:oafocient. r alays signjflcantly dif("rant from tero at O.OS level (Fhlher's Z-test). others (8), hich indicates that path-trace reslts provide i reasonable basis against hich to compare the srvey method reslts. VALDATON OF STUDY RESULTS n presenting the reslts of the validation stdy, to different types of analyses are described. The first is a comparison of the performance measre smmary statistics obtained for each of the 5 data sets (i.e., the 5 combinations of srvey site, srvey time, and lane configration). The second analysis is a comparison of the freqency distribtion predicted and observed for each of the performance measres. n presenting these reslts, only those obtained by sing the expanded srvey method are shon (i.e., by sing the srvey form shon in Figre 2), For the stdy sites, there as no appreciable difference beteen reslts obtained by sing either of the srvey forms, mainly becase each intersection as isolated from pstream intersections and hence the arrival rates in the red and green periods ere approximately eqal. t shold also be noted that there as no difference beteen reslts obtained by sing the srvey method in the field and in the laboratory (see, for example, Figre 3). This implies that there as little or no observer error in recording qee lengths or signal timings in the field. ndependent comparison of qee-length estimates in the field and in the laboratory confirmed this impression, althogh qee-length estimates in the field ere marginally smaller than those in the laboratory. Signal-timing observations in the field ere also qite accrate. t shold be noted, hoever, that digital stopatches ere sed in the field srveys and this eliminated many timing errors that might have occrred if normal rist atches had been sed for timing. Also, the data-entry program sed in QDELAY atomatically detects obvios timing errors and allos for correction of these errors. A more complete description of the comparison beteen srvey method reslts obtained in the field and in the laboratory may be fond elsehere (16). To examine the theoretical error in the srvey method calclations, a comparison of smmary statistics is presented both in tablar and graphical fashion. Table 1 smmaries the reslts of regression analyses condcted hen measres of delay, stops, and vehiclar volme obtained from the srvey method in the laboratory ere compared ith the same measres obtained from the path-trace method. These regression analyses ere condcted ith all 5 data sets (i.e., both sites, all times of day, and all lane configrations), each contribting one data point to the analysis. The regression eqation sed as of the form Y= a+ bx (1) here Y s X a,b performance measre obtained from the srvey method in the laboratory, performance measre obtained from the pathtrace method, and estimated regression coefficients. AS can be seen in Table 1, most measres ere predicted by the srvey method ith a high degree of consistency, as indicated by the high vales of r 2, More importantly, the srvey method and the path-trace method give nearly eqal vales of the performance measres, as indicated by the high vale of E. This vale, termed the coefficient of effi-

5 45 ciency (19), may be sed to test for bias in the regressionrelation. f the reslts from the srvey method and the path-trace method are highly correlated bt biased (i.e., the data points do not lie evenly arond the Y = X line), then E ill be mch less than r 2, f there is no bias in the rela- Figre 4. Comparison of average approach delays. 2 o DATA PONT' BEACONSFELD PDE, _.. DATA PONT : NCHOLSON STREET % CONFDENCE LMTS FOR MEAN 4 6 AVERAGE APPROACH DELAY (SECONDS) ( METHOD) Figre 5. Comparison of standard deviations of approach delay,,o ;: li 4 -lil.,,., o - Wo 3 lllo -:1: >>-- ""' _,::;,_ o., :1:> 2 "' <:, o"' J: a.,-..<!) <Z > "' :, o"',_::i vi8 1 /.f,v hv /,(,,;' i;,{'. Jt Figre 6. Comparison of average stopped delays. o DATA PONT' BEACONSFELD PDE DATA PONT, NCHOLSON STREET ---95% CONFDENCE LMTS FOR MEAN STD, DEV APPROACH DELAY (SECONDS) ( METHOD) 6-r ,...-?-. tion, then E = r 2, With the exception of the regression for the standard deviation of the nmber of stops per vehicle, the high vales of r 2 and E indicate excellent agreement beteen the srvey method and path-trace reslts. TWO other indications of the agreement beteen the to srvey methods may be seen in the sie of the intercepts and slopes of the regression lines. f there as perfect agreement beteen the to methods, the intercept old be eqal to ero and the slope old be eqal to one. t can be seen that, in most cases, the 95 percent confidence limits inclde the desired vale of either the intercept or the slope, hich indicates excellent agreement. The conclsions that may be dran from Table 1 may be reinforced by reference to Figres 4 throgh 7, hich sho the data points, regression lines, and confidence limits for a nmber of different performance measres. For each of the measres shon, hich are the most important otpts of the srvey method, it is obvios that there is qite good agreement beteen the to methods of collecting data on intersection performance, The second type of analysis of the reslts is to compare the freqency distribtions of the performance measres obtained from each of the srvey methods, n comparing these distribtions for ap- Figre 7. Comparison of nmber of complete stops per vehicle. >-... <( o ct J: o a. J: ti :;,-.,_ Vl. > ffi <DJ: ::;,-. <!> 2-, ,......,,Ao oq, - 69,<",<,,,.,,,,.. o DATA PONT, BEACONSFELD PDE W DATA PONT' NCHOLSON STREET. ffi --- 9%CONFDENCE LMTS FOR MEAN ,--""T'"--r---r ,--""T'"--r---! 1 2 AVERAGE NUMBER OF STOPS PER VEHCLE ( METHOD), Figre 8. Comparison of approach-delay distribtions (Nicholson Streed. NCHOLSON ST.. PEAK LANE ONE >- " 3. qq.,,- -o?i _,>-- >- a.... Vl J:... <( 8 D 2 o DATA PONT' BEACONSFELD PDE DATA PONT, NCHOLSON STREET % CONFDENCE LMTS FOR MEAN 3 4!Q 6 AVERAGE STOPPED DELAY ( SECONDS) ( METHOD)... 6 a. > ;:: < 4 ::; 2-3,,,.,/, LAB. MODEL 2 STANDARDZED VALUE OF APPROACH DELAY 3

6 46 Figra 9. Comparison of approach-delay distribtions (Beaconsfield Parada) "' " "'. "' > ;: < :, BEACONSFELD PARADE LANES ONE, TWO ANO THREE 1, =;;;;;;=-, / t 7 6 / qo 2,," LAB MODEL -3-2 _, 2 3 STANDARDZED \ALUE OF APPROACH DELAY Figra 1. Comparison of stopped-delay distribtions (Nicholson Streat). NCHOLSON ST PEAK LANE ONE preach delay and stopped delay, the analysis as condcted separately for each site, time of day, and lane across stop line. Althogh it is not possible to present all these reslts [see Richardson and Graham (16)], Figre 8 and 9 sho typical reslts for approach delay obtained for Nicholson Street and Beaconsfield Parade, respectively. t is clear that the agreement beteen the shape of the distribtions is better at the Nicholson Street site, althogh it is far from poor at Beaconsfield Parade. Note that the reslts shon for Beaconsfield Parade are for the case here all three lanes are combined in the one data set, ths necessitating the se of a representative end-of-qee vehicle, as described earlier. At both sites, the approach-delay distribtion shos a characteristic ske to the right. The distribtions of stopped delay for typi cal cases at both sites are shon in Figres 1 and 11. Again it can be seen that Nicholson Street data prodce better agreement than Beaconsfield Parade data, hen the proportion of vehicles that sffer no stopping delay is slightly overpredicted by the qeelength srvey method. Hoever, considering that the distribtions from the qee-length srvey method are synthesied fro the relatively simple inpt data hereas the path-trace distribtions are constrcted from measres of individal vehicle performance, the agreement beteen the distribtions is qite satisfactory.... "'.. 6 "'. "' >.:: < :, LAB. MODEL STANDARDZED \ALUE OF STOPPED DELAY CONCLUSON This paper has described the validation of a srvey method for the measrement of performance at signalied intersections. The inpt and otpt of the method have been described and some featres of the analysis program have been discssed. The condct of the validation stdy has been described and some of the reslts of the stdy are presented. On the basis of the reslts presented (and those contained in other, more complete, reports), it is conclded that the srvey method prodces a ide array of otpt statistics to a high degree of accracy (hen compared to observations by sing a path-trace method). Despite the comprehensive natre of the otpts, the inpt to the srvey method is relatively simple and reqires fe resorces in terms of. personnel and eqipment. t is anticipated that the srvey method shold find ready application in many signalied intersection srvey stdies. ACKNOWLEDGMENT Figra 11. Comparison of stopped-delay distribtions (Beaconsfield Parade). BEACONSFELD PARADE LANES ONE, TWO 6 THREE The validation financed by a Road Research acknoledged. stdy described in this research grant from the Board. This spport is paper as Astralian grateflly REFERENCES... "' a: "'. "' >.:: < GO L AB. MODEL 2 3 STANDARDZED \ALUE OF STOPPED DELAY 1. B.D. Greenshields. A Photographic Method of nvestigating Traffic Delays. Proc., Michigan Highay Conference, 1934, 2. D.S. Berry and C.J. van Til. Comparison of Three Methods for Measring Delay at ntersections. Traffic Engineering, vol. 25, 1954, pp , 3, D.S. Berry. Field Measrement of Delay at Signalied ntersections. Proc., HRB, Vol. 35, 1956, pp , G,S. Sagi and L,R. Campbell. Vehicle Delay at Signalied ntersection: Theory and Practice. Traffic Engineering, 1969, pp , H, Sofokidis, D,L. Tilles, and D.R. Gerger. Evalation of ntersection-delay Measrement Techniqes. HRB, Highay Research Record 4 53, 1973, pp

7 H.D. Robertson and W.G. Berger. A Manal Techniqe for Measring ntersection Delay. Traffic Engineering and control, Vol. 17, Oct. 1976, pp M.G. Behler, T.J. Hicks, and D.S. Berry. Measring Delay by Sampling Qee Backp. TRB, Transportation Research Record 615, 1976, pp W.R. Reilly, c.c. Gardner, and D.H. Kell. A Techniqe for Measrement of Delay at ntersections. FHWA, Final Rept., NTS: PB A.J. Richardson and K.W. Ogden. An Evalation of Active Bs-Priority Signals. TRB, Transportation Research Record 718, 1979, pp A.J. Richardson. Measrement of the Performance of Signalied ntersections. TRB, Transportation Research Record 699, 1979, pp W.R. Reilly. comments on Measrement of the Performance of Signalied ntersections by A.J. Richardson. TRB, Transportation Research Record 699, 1979, p. 59. N.R. Graham and A.J. Richardson. A Revie of Measres of Signalied ntersection Performance. Monash Univ., Clayton, Victoria, Astralia, Civil Engineering Working Paper /5, 19. N.R. Graham and A.J. Richardson. Signalied ntersection Srvey Method: Validation Srvey Design and Administration. Monash Univ., Clayton, Victoria, Astralia, Civil Engineering orking Paper /15, A.J. Richardson. Signalied ntersection Srvey Method: Theoretical Backgrond. Monash Univ., Clayton, Victoria, Astralia, Civil Engineering Working Paper /13, A.J. Richardson. Signalied ntersection Srvey Method: Field Srvey sers Manal. Monash Univ., Clayton, Victoria, Astralia, Civil Engineering Working Paper /14, A.J. Richardson and N.R. Graham. Signalied ntersection Srvey Method: Empirical Reslts of Validation Stdy. Monash Univ., Clayton, Victoria, Astralia, Civil Engineering Working Paper /16, A.J. Richardson and N.R. Graham. Objectives and Performance Measres in Urban Transport Systems. Seminar on Fel Consmption, Vehicle Emissions, Traffic Management, and Vehicle Design; Society of Atomotive Engineers, Astralia, and the Astralian Road Research Board, R.E. Allsop. Delay at a Fixed Time Traffic S ignal--part : Theoretical Analysis. Transportation Science, vol. 6, No. 3, 1972, pp A.P. Aitken. Assessing Systematic Errors in Rainfall-Rnoff Models. Jornal of Hydrology, vol. 1, 1973, pp Pblication of this paper sponsored by Committee on Methodology for Evalating Highay mprovements. Compter-Controlled Videotape Display: An nnovation in Traffic Analysis KENNETH A. BREWER AND WLLAM F. WOODMAN Althogh videotape eqipment has been available to traffic researchers and engineers for over a decade, its ses have been limited to rotine applications. Hoever, the recent development of microcompters and interface eqipment facilitate the se of videotape (and videodisc) in research applications. Crrent research nder contract to the oa Department of Transportation is detailed here compter-videotape simlations of ncontrolled intersections elicit responses by a sample dran from a pblic location. Data are presented to demonstrate (a) the efficacy of the videotape-compter research approach as ell as (bl sefl findings that sggest the presence of ord-oriented verss symbol-oriented sbgrops in the adlt poplation, each having very different responses to varios arning signs. Television and videotape have been sed as traffic engineering data-collection tools in a variety of ays ithin the past decade as portable camera-recorder systems became generally available (.!-11 Some of these ses have inclded collecting data on the speed of vehicles; lane placement of vehicles: license-plate vehicle identification for monitoring vehicles throgh a portion of a system: accident srveillance on bridges, tnnels, and freeays: and emergency traffic operations coordination. Videotape is being commonly sed in edcation and training activities. This se is not, hoever, as extensive as is commonly thoght by persons otside of edcation. n this paper, e presme sch se to be common knoledge. n a similar fashion, the general availability of small personal compters (32K-64K memory) for se in both traffic engineering and edcation activities is assmed to be common knoledge. What is ne on the technological scene is an interface board to permit a microcompter to control a ne generation of video player-recorders. This combination provides a ne analysis tool (11 This paper otlines ho this ne tool has been incorporated- into an innovative analysis of rral road signing throgh some creative compter programming. PROBLEMS N SGNNG Several oa conties ere frstrated in their attempts to commnicate ith people driving their extensive netork of lo-volme gravel rral roads. When these lo-volme gravel roads intersect in the rolling oa terrain, a variety of factors interact to create seasonal (or sometimes continosly) hidden intersections. Some examples inclde the folloing: 1. Tall corn groing, planted to the very edge of the right-of-ay (or perhaps in the right-of-ay): 2. Trees at farmsteads in the corner qadrants of the intersecting roads; 3. Sharp crves ithin narro cts: 4. Densely ooded areas on crves; and