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HomeMy WebLinkAboutOB 1 SIGNAL WARR STDY 12-3-84AGE OLD BUS[NESS NO. 1 NDA DATE NOVEMBER 28, 1984 TO: FROM: SUBJECT: WILLIAM HUSTON, CITY MANAGER BOB LEDENDECKER, DIRECTOR OF PUBLIC WORKS/CITY ENGINEER TRAFFIC SIGNAL/STOP SIGN WARRANT STUDY FOR MCFADDEN AND MYRTLE AVENUES RECOMMENDATION: Receive and file. No other action required. BACKGROUND: On November 5, 1984, the City Council requested staff to complete a warrant study for either a traffic signal installation or a four-way stop installation at the intersection of McFadden and Myrtle Avenues. DISCUSSION: The attached warrant studies have been completed by the city's Traffic Engineer Consultant and are self-explanatory with respect to each study. As indicated in these studies, none of the warrants for either signalization or a four-way stop sign installation were met for the subject intersection. Bob Ledendecker Director of Public Works/City Engineer BL:jr Attachment Inter-Corn DATE: NOVEMBER 27, 1984 FROH: S UBJ ECT: BOB LEDENDECKER, DIRECTOR OF PUBLIC WORKS/CITY ENGINEER JIM KAWAMURA, CONSULTING TRAFFIC ENGINEER TRAEFIC SIGNAL & STOP SIGN WARRANTS FOR THE INTERSECTION OF MCFADDEN STREET/MYRTLE AVENUE Per your directive, studies were conducted to determine: 1) whether or not a traffic signal was warranted for the subject intersection; and 2) whethere or not stop signs were warranted on McFadden Street at the subject intersection. Traffic counters were placed at the subject intersection for a 24-hour period commencing at 8:00 a.m. on November 14, 1984. (See attached machine count summaries). Intersection accident data for the past 3 1/2 years were compiled in the form of collision diagrams. (See attached). This data was utilized along with the traffic counts, field measurements, and observations to determine whether necessary warrants were me% for signalization or stop signs. Signalization The standard traffic engineering practice in determining whether or not a particular intersection should be signalized is to follow the warrants criteria established by CalTrans in Chapter 9, "Traffic Signal and Lighting", of the State Traffic Manual. (See attached excerpts.) Utilizing the collected data the warrant sheets provided in the Traffic Manual were filled in. (See attached "traffic signal warrants".) As indicated, none of the warrants for signalization of the subject intersection are met..Traffic would have to increase substantially in order.to justify signalization. In fact, the volume of traffic on Myrtle Avenue would have to more than double to meet even one warrant (i.e., the "interruption of continuous traffic" warrant). It should be noted that this is highly unlikely given the nature and build out of the residential development along Myrtle Avenue. It should be further noted that satisfaction of a warrant is not necessarily justification for signalization. Excessive delay,, congestion, safety problems, and other factors must be established as well. Stop Signs The policy and criteria for the installation of stop signs are established by CalTrans in Chapter 4, Section 4-03.3 of the Traffic Manual. (See attached excerpt). TRAFFIC SIGNAL & STOP SIGN WARRANTS FOR THE INTERSECTION OF MCFADDEN STREET/MYRTLE AVENUE NOVEMBER 27, 1984 PAGE 2 None of the conditions warranting a four-way stop are met at the subject intersection: a) a four-way stop would not serve as an interim measure for signalization since traffic signals are not warranted; b) there have not been five or more accidents during a 12-month period which could have been prevented if a four-way stop were in place; c) minimum volumes of 140 vehicles or pedestrians per hour for eight hours on the minor street (Myrtle Avenue) are not. met; and, d) traffic volumes on the approach legs are not approximately equal. Since the proportion of vehicles on McFadden Street verses Myrtle Avenue is more than fifty to one during certain hours, the placement of stop signs on McFadden Street at Myrtle Avenue would cause severe delay and congestion not to mention constant violations by impatient drivers. Conclusions The subject intersection does not meet warrants for signalization or for stop signs on McFadden Street.' The subject intersection has adequate visibility and lighting, and the minor delays and accidents experienced at the subject intersection are not any worse (or better) than other similar intersections in the city. As a mitigating measure to the problems encountered by Myrtle Avenue residents, enforcement of speed limits on McFadden Street could make access to and from Myrtle Avenue less troublesome and perhaps safer. Improved coordination of the 'existing signals along McFadden Street may also help. The latter measure will be investigated further, and if deemed appropriate, implemented in the field. JimlKawamura Consulting Traffic Engineer JK:jr FORM TC-g TRAFFIC COUNTING MANUAl MACHINE COUNT .~D[ BY ..... DAli J-L"i-§':~-~. CHECKED BY ..... DATE ......... ~,UMMARY TYP OF COUNT~ ~ DIRECTIONAL J ] Z-WAY DATE BEGUN DIRECTION; DATE DAY', ~_2 - 2-3 3-4 '" 2-3 5-6 ~ ~ M. ~-]o TOTAL AoM¸ FORM TC-9 TRAFFIC COUNTING MANUAL MACHINE COUNT MA0[ BY ..... D~,T[ _~_{_~l_5'_:.~_~l~_ ~,~ECKED BY ..... DATE SUMMARY CONDUCTED ONt.- ~C~~ ~/O ~Y~T~- ~(~ ~ DIRECTIONAL ~ Z-WAY DATE BEGUN ~[~ [~ TYPE 131' [,UUm~; ~ ~" ............. DIRECTION '--~~ DAY, 12-1 i-2 2-3 3-4 5'-6 r~l ,A.~ 7-8 8-9 , 9-1o, lO-q] -~7~ 707~ s-~ ~74 ~-~ 7~0 5-6 ~lO P.~ M. 7-e 41,/. e-9 274 9-~o 11-12 f~.~ TOTAl- A.M P. fORM TC-9 ERAFEIc COUNTING MANUAL A.M MACHINE COUNT SUMMARY /~(o CHECKED BY ..... DATE 1 Yl"iff.. UI' ~..uum DIRECTION -DAte I I-- {4--0-~ ~2-~ 2-3 3-4 4-5 2-3 4-5 7 TOTAL CONDUCTED ON*" ~/'~'~"~"{'~----~- [~ DIRECTIONAL FORM TC-9 TRAFFIC COUNTING MANUAL SUMMARY ~HECKED BY ..... DATE ......... CONDUCTED ON: /,,/t,~'~'['-~.~, ....~/~ ~v~c,i~_-,~j,....) TYPE OF COUNT: ~ DIRECTIONAL [--] ?-wAY DATE BEGUN D,RECT,O.; DAY, 2-3 O. 3-4 '2~ 4-s 3-4 Z~. _ 4-~ ~-9 9-10 1~!1 TOTAL ~LLISION DIAGR3~{ iTY OF TUSTIN LEGEND-SYMBOLS Moving Vehicle ~ Backing Vehicle ~ Out of Control ~ Parked Vehicle__ ~ Pedestrian ---~ Fixed ~bject ~ No~-In3ury In3ury O~ Fata~ DaYlxght t~ LOCATION: ACCIDENT SL~dMARY TYPE DAY NIGHT TOTAL Fatal Inj. P.D. Fatal lInj':'~.D. Fatal' Inj.] P.D. Right Angle ... _._ Rear End --. Left Turn :, Sideswipe _ .Pedes.tria~ Other COLLISION DIAG PJ~ ITY OF TUSTIN LEGEND-SYMBOLS. Moving Vehicle Hacking vehicle Out of Control Parke~ Vehicle---~ Pedestrian Fixed Object og-xnjury In]ury Fatal Daylight ACCIDENT SUMMARY TYPE DAY NIGHT TOTAL Fatal Inj.! P.D'. Fatal In)'. P.D. Fatal'iInj. P.D. --Right An~le Rear End Left Turn F Side swi~e Pedestriaq .... Other C~LLI$ION DIAGRAM _.TY OF TUST~N LEGEND-SYMBOLS Moving Vehicle ~ Backing Vehicle ~ Out of Control ~ Parked Vehicle ~ Pedestrian ---~ Fixed Object i No~-Injury O~ In]ury Fatal · Daylight~rk C~_ I ACCIDENT SUMMARY TYPE DAY NIGHT TOTAL Fatal Inj. P.D. Fatal Inj. P.D. Fatal Inj.! P.D. --Right Angle Rear End Left Turn Sideswipe -- Pedestrian Other ~ITY OF TUSTIN LEGEND-SYMBOLS Moving Vehicle Backing vehicle Out of Control Parked Vehicle Pedestrian Fixed Object Non.-Injury Daylight LOCATION: ~¢F~DDE~ ~ /VYR:4E. '3 /-,'~'- ?/- c. ... R ACCIDENT SUMMA Y TYPE DAY NIGHT TOTAL Fatnl Inj. P.D. Fatal Inj. P.D. Fatal Inj. P.D. -- Right'Angle - Rear End .. Lc'it Turn Sideswipe Pedestrian - Other Traffic Manual TRAFFIC SIGNALS AND LIGHTING 9-1 12-19/9 CHAPTER 9 TRAFFIC SIGNALS AND LIGHTING Traffic Signals-Basic Information and Warrants 9-01 9-01.1 Introduction Traffic signals are electrically powered' traffic con- trol devices which alternately direct traffic to stop and proceed at highway and street intersections. Their purpose is the orderly assignment of right of way to the various traffic movements. When justified and properly designed, a traffic sig- nM installation may achieve one or more of the fol- lowing: 1. Reduce the frequency of certain types of acci- dents; especially the right-angle type; 2. Effect orderly traffic movement; 3. By proper coordination, the continuous flow of a platoon of traffic at a definite speed along a given route; 4. Allow other vehicles and pedest~ans to cross a heavy traffic stream; and 5. Control traffic more economically than by man- ual methods. Unjustified, ill-designed, improperly-operated, or poorly maintained traffic signals may cause: 1. Increased accident frequency, 2. E~xcessive de{ay, 3. Disregard of signal indications, and 4. Circuitous travel by alternate routes. Contrary to common belief, traffic signals do not always increase safety and reduce delay. Experience shows that the number of fight-angle collisions may decrease after the installation of signals, but the num- ber of rear-end collisions will increase in many in-. stances. The instal}ation of signals may increase over- all delay and reduce intersection capacity. Consequently, it is of the utmost importance that the consideration of a signal installation and the selection of equipment be preceded by a thorough study of traffic and roadway conditions made by an engineer experienced and t-rained in this field. Equally impor- tant is the need for checking the efficiency of a traffic signal in operaHon. This determines the degree to which the type of installation and the timing pro- gram meets the requirements of traffic. 9-01.2 Warrants The warrants for the installation of traffic signals are based on those stated in the Manual on Uniform Traffic Control Devices. These warrants apply to both pre-timed and traffic-actuated traffic signals. When the 85-percentile speed of major street traf- fic exceeds 40 miles per hour, or when the intersec- tion lies within the built-up area of an isolated eom- munity having a population less than 10,000, the location is considered rural. All other areas are con- sidered urban. Since the installation of traffic signals may increase certain types of collisions, the decision to install signals should not be based solely upon war- rants. Consideration should also be given to such fac- tors as delay, congestion, approach conditions, driver confusion and additional evidence of need for right of way assignment above that which could be 'pro- vided by stop signs. The installation of traffic signals should be consid- ered ff one or more of the warrants listed below are met: Warrant 1 - Minimum Vehicular Volume. Warrant 2 - Interruption of Continuous Traffic. Warrant 3 - Minimum Pedestrian Volume. Warrant 4 - School Crossings. Warrant 5 - Progressive Movement. Warrant 6 - Accident Experience. Warrant 7 - Systems. Warrant 8 - Combination of Warrants. 9-01.3 Warrant I -/Y~inimum Vehicular Volume The minimum vehicular volume warrant is intend- ed for application where the volume of intersecting traffic is the principal reason for consideration of sig- nal installation. The warrant is satisfied when for each of any 8 hours of an average day the traffic volumes given in the table below exist on the major street and on the higher-volume minor street ap- proach to the intersection. Number of lanes for moving traffic on each approach Major Street 2 or more -- Vehicles per Vehicles per hour on major hour on higher- street (total volume minor- of both stre et approach approaches) (one direction only) (Minimum Requirements) Minor Street Urban Rural Urban Rural I ....... 500 350 150 1 ....... 600 420 150 105 2 or more -- 600 420 200 140 2 or more -- 500 350 200 140 ~-2 TRAFFIC SIGNALS AND LIGHTING Traffic Manual 12-197~ The major street and the minor street volumes are for the same 8 hours. During those 8 hours the direc- tion of higher volume on the minor street may be on one approach during some hours and on the opposite approach during other hours. Left turn movements from the major street may be included with minor street volumes if a separate signal phase is to be provided for the left turn move- ment. The left turn volume in the highest direction may be added to the minor street volume on the highest approach and the major street volume should be reduced by this amount. 9-01.4 Warrant 2 - Interruption of Continuous Traffic The interruption of continuous traffic warrant ap- plies to operating conditions where the traffic vol- ume on a major street is so heavy that traffic on a minor intersecting street suffers excessive delay or. hazard in entering or crossing the major street. The warrant is satisfied when for each of any 8 hours of an average day the traffic volumes given in the table below exist on the major street and on the higher- volume minor street approach to the intersection, and the signal insta]lation will not seriously disrupt progressive traffic flow. Number of lanes for moving traffic on each approach Major Street Vehicles per Vehicles per · hour on major hour on higher- street (total volume minor= of both street approach npproachea) (one direction only) (Minimum Requirements) Minor Street Urban Rural Urban Rural I ...... · ~ I ....... 750 525 75 53 2 or more -- 1 ....... 900 630 75 53 2 or more -- 2 or more -- 900 630 100 70 I ....... 2 or more -- 750 525 100 70 The major street and minOr street volumes are for the same 8 hours. During'those 8 hours the direction of higher vol-me on the minor street may be on one approach during some hours and on the opposite approach during other hours. Left tufa movements from the major street may be included with minor street volumes if a separate signal phase is to be provided for left turn move- ment. The left turn volume in the highest direction may be added to the minor street volume on the highest approach and the major street volume should be reduced by this amount. 9-01.5 Warrant 3 - Minimum Pedestrian Volumo The minimum pedestrian volume warrant is satis- fied when for each of any 8 hours of an average day the following traffic volumes exist: 1. On the major street 600-Urban, 4,qG-Rural or more vehicles per hour enter the intersection (total of both approaches): or 1,000-Urban, 700 -Rural or more vehicles per hour (total of both approaches) enter the intersection on the ma- jor street where there is a raised median island four feet or more in width; and 2. During the same 8 hours as in paragraph 1., there are 150-Urban, 105-Rural or more pede- strians per hour on the highest volume cross- walk crossing the major street. A signal installed under this warrant at an isolated intersection should be of the traffic-actuated type with push buttons for pedestrians crossing the main street. If such a signal is installed at an intersection within a signal system, it should be equipped and operated to provide proper coordination. Signals instal]e~ according to this warrant shall be equipped with pedestrian indications conforming to requirements set forth in other sections of this Man- ual. Signals may be installed at nonintersection loca- tions (Mid-block) provided the requirements of this warrant are met, and provided that the related cross- walk is not closer than 150 feet to another established crosswalk. Curbside parking should be prohibited for a minimum of 100 feet in advance of and 20 feet beyond the crosswalk. Phasing, coordination and in- stallation must conform to standards set forth in this. Manual. Special attention should be given to the sig- nal head placement and the signs and markings used at nonintersection locations to be sure drivers are aware of this special application. 9-01.6 Warrant 4- School Crossings See Ghapter 10. 9-01.7 Warrant 5- Progressive Movement The progressive movement warrant is satisfied when one of the fo]lowing is true: 1. On a one-way street or on a street which pre- ponderantly has unidirectional traffic signifi- cance, adjacent signals are so far apart that the necessary degree of platooning and speed eon- trol of vehicles would otherwise be lost or, 2. On a two-way street, where adjacent signals do not provide the necessary degree of platooning and speed control and the proposed and adja- cent signals could constitute a progressive signal system. The installation of a signal according to this war- rant should be based on the 85-percenlile speed un- less an engineering study indicates that another speed is more desirable. The installation of a signal according to this war- Traffic Manual TRAFFIC SIGNALS AND LIGHTING 9-3 12-1979 rant should not be considered where the resultant signal spacing would be less than 1,000 feet. 9-01.8 Warrant 6-Accident Experience The accident-experience warrant is satisfied when: 1. Adequate trial of less restrictive remedies with satisfactory observance and enforcement has failed to reduce the accident frequency; and 2. Five or more reported accidents of types sus- ceptible of correction by traffic signal control have occurred within a lg-month period, each accident involving personal,injury or property damage to an apparent extent of $200 or more; and 3. There exists a volume of vehicular and pedes- trian tralYic not less than 80 percent o[r the re- quirements specified in the minimum vehicular -volume warrant, the interruption of continu- ous traffic warrant, or the rnL,~rnum pedestrian -volume warrant; and 4. The signal installation ~ not seriously disrupt- progressive traffic flow. 9-01.9 Warrant 7- Systems Warrant A traffic sign~! installation at some intersections may be warranted to encourage concentration and organization of traffic flow networks. The systems . warrant is applicable when the common intersection of two or more major routes has a total existing, or iramediately projected, entering volume of at least 800 vehicles during the peak hour o£ a typical week- day, or each of any five hours of a Saturday and/or Sunday. A major route as used in the above warrant has one or more of the following characteristics: 1. It is part of the street or highway system that · serves as the principal network for through tra~- fie flow; 2. It connects areas of principal traffic generation; 3. It includes rural or suburban highways outside of, entering Or traversing a city; 4. It has suri~ace street freeway or expressway ramp terminals; ~ 5. It appears as a major route on an official plan such as a major street plan in an urban area traffic and transportation study. 9-01.10 Warrant 8-Combination of Warrants In exceptional cases, signals occasionally may be justified where no single warrant is satisfied but where any two of Warrants 1, 2 and 3 are satisfied to the extent of SO percent or more of the stated numer- ical values lror each of any 8 hours of an average day. 9-01.!1 Periodic Traffic Signal Studies To maintain the desirable operation of existing traffic signals, it is necessary to periodically conduct engineering studies to ensure that the desired opera- tion is realized. In particular, engineering studies should determine whether the installation continues to be justified and that the signal timing in use meets the current traffic requirements. 9-4 TRAFFIC SIGNALS AND LIGHTING Traffic Manual 12-1979 Figure 9-1A TRAFFIC SIGNAL WARRANTS CALC DATE CHK DATE DIST CO RTE PM Major St: 4/~/_" Critical Approach Speed Minor St: ~ Critical Approach Speed Critical speed of major street traffic--> 40 mph ............. I-I In built up area of isolated community of < 10,000 pop. - ....... ~ RURAL (R) URBAN (U) mph mph WARRANT I - Minimum Vehicular Volume MINIMUM REQUIREMENTS 100% SATISFIED Yes U No {80% SHOWN IN SRACKEI'S) 80e/e SATISFIED Yes ~j~ Strut (400) (~0) (4~) 336) Hig~st ~Y 1~ 105 ~ "NOTE: Heavier of left turn movement from Major Street included when L T-phasing i? proposed WARRANT 2 -- Interruption of Continuous Traffic MINIMUM REQUIREMENTS 100% SATISFIED Yes 1'3 No J~ U I R U I R 80~/~ SATISFIED Yes [] No r~ ~j~ Strut (~0) (4~) (720) (504) Minor Str.t' (60) (42) (00) (56) ~ ~7 Jg J~I ~7 ~ ~ ~ * NOTE: Heavier of left turn movement fro~ Major Street included when I_T-phasir.g Is proposed I--I WARRANT 3 - Minimum' Pedestrian Volume 100°,( SATISFIED Yes [] No D MINIMUM REQUIREMENTS 80°~ SATISFIED Yes [] No I-~ (80% SHOWN IN BRACKETS) u R / / / / / / / Both Apprch~. NO Median 600 420 ~lajor Street (4801 (336I Raised 1000 700 Volume 4' Median (800) Is60) Ped's On Highest Volume 150 105 X-Walk Xin~ Ma. joE Street (126 ~84) IF MIDE~*,.OCK SIGNAL PROPOSED [:] MIN.150NEQUiR[MENTFeet 1DISTANCE TO NEAREST ESTASL ISHED CRWLK'IN/E ft S/W ft Yes FULFILLEDD NO WARRANT 4 - School Crossings Not Applicable r-I See School Crossings Warrant Sheet D TS-IOA Hour Hour Traffic Manual TRAFFIC SIGNALS AND LIGHTING 9-5 ~, 12-1979 Figure 9:1B' TRAFFIC SIGNAL WARRANTS WARRANT 5 -- Progressive Movement Satisfied Yes [] No ~ MINIMUM REQUIREMENTS1 DISTANCE TO NEAREST SIGNAL FULFILLED > 100Oft' [N /t//,,~,S /V//,~ ft, E /2.DO ft, W -~ ft YESE] NOJ~ ON ISOLATED ONE WAY ST, OR ST. WITH ONE WAY TRAFFIC SIGNIFICANCE ADJACENT SIGNALS ON 2-WAY ST, WHERE ADJACENT SIGNALS DO NOT PROVIDE NECESSARY PLATOONING & SPEED CONTROL. PROPOSED SI, GNALS COULD CONSTITUTE A PROGRESSIVE SIGNAL SYSTEM [--I ~J WARRANT 6 - Accident Experience Satisfied Yes n No ~ REQUIREMENT WARRANT ~' FULFILLED ONE WARRANT WARRANT I -- MINIMUM VEHICULAR VOLUME .o~ --=" ........ ~ESO .OB WARRANT S - MINIMUM PEDESTRIAN VOLUME SIGNAL WILL NOT SERIOUSLY DISRUPT PROGRESSIVE TRAFFIC FLOW ADEQUATE TRIAL OF LESS RESTRICTIVE REMEDIES NAS FAILED TO REDUCE ACC. FREQ, [] [] ACC WITHIN A 12 NON. PERIO~ SUSCEPTIBLE OF CORR. ~ INYOLWNGINJURY OR~S~ODAMAG[ MINIMUM "EQUI"EMEN* NUMBE" OF ACCIDENTS ' NOTE: Left turn accidents can be included when LT-phasing is proposed WARRANT 7 - Systems Warrant Satisfied Yes [] No ~ MINIMUM VOLUME REQUIREMENT ENTERING VOLUMES - ALL APPROACHES ~/ FULFILLED DURING TYFICAL W[ KOAY PEAK HOUR .. ~'-~0 vrH/xn gO0 YEN/HR CHARACTERISTICS OF MAJOR ROUTES ~R ST~MINORS1 PART OF HWYSYST[M $[RVINGAS PRINCIPLE NETWORKFOR THOUGH TFC APPEARS AS M~R ROUTE ON AN OFFICIAL PLAN ANY MAWR ROUTE CHARACTERISTICS MET. lOTH STS. WARRANT 8 -- Combination of Warrants (Used if no one warrant satisfied 100~) Satisfied Yes [] No ~ REQUIREMENT WARRANT ~/]FULFILLED e0% 3 -- MINIMUM PEDESTRIAN ¥O~UME YES[] NO ~ The satisfaction of a warrant is not necessarily justification for signals. Delay, congestion, confusion or other evidence of the need for right of way assignment must be shown. 4-22 SIGNS TRAFFIC MANUAL April 1975 I I Doslgn, Policy and Location for Individual Signs White on Red 30' octagon 10' Series C lenerl (Also available in 24', 36' and 48' sizes) Policy: The RI sign shall be used on public roads where a stop is required. Stop signs shall be erected on both the left and right side of one-way roadways which are 30 feet or more in width. Stop signs shall not be installed at signalized intersections. Conditions warranting STOP signs are: 1. On the less important road at its intersection with a main road where application of the nor- mai right of way rule is unduly hazardous as evidenced by accidents susceptible of correc- tion by STOP signs. g. On a county road or city street at its intersec- tions with a state highway. 3. At the intersection of two main highways. The highway traffic to be stopped depends on ap- proach speeds, volumes, and turning move- ments. 4. On a street entering a legally established through highway or street. 5. On a minor street where the safe approach speed to the intersection is less than l0 miles per hour. ' A STOP sign is not a "cure-all" and is not a substi- tute fo~ other traffic control devices. Many times the need. for a STOP sign can be eliminated if the sight distance is increased by removing obstructions. The installation of STOP signs at locations where they are unexpected or where approach speeds are high should be avoided if possible because they may increase accidents. However, ff there is no alterna- tive to. a STOP sign, then an advance Code WI7 STOP AHEAD sign and appropriate pavement markings should be placed in conjunction with it. Publicity through the radio and press is highly de- sirable when STOP signs are installed and especially when it is necessary to change their location. Any of the following conditions may warrant a four-way stop sign installation: 1. Where traffic signals are warranted and the need is urgent, the four-way stop is an interim measure that can be installed quickly to control traffic while arrangements are being made for the signal installation. g. An accident problem, as indicated by five or more reported accidents of a type susceptible of correction by a four-way stop installation in a 12-month period. Types of accidents susceptible of correction include right angle and left turn collisions. 3. Minimum volume warrant: a. The total vehicular volume entering the in- tersection from all approaches must average at least 500 vehicles per hour for any eight hours of an average day, and b. The combined vehicular and pedestrian vol- ume from the minor street or highway must average at least 200 units per hour for the same eight hours with an average delay to minor street vehicular traffic of at least 30 seconds per vehicle during the maximum hour. e. When the &5-percentile approach speed of the major street traffic exceeds 40 miles per hour, the minimum vehicular volume war- rant is 70 percent of the above requirements. A four-way stop sign installation is a useful traffic control measure when other available means of eon- trol are not adequate. It should not be used unless the volume of traffic on the intersecting roads is about equal and is undesirable at low-volume intersections. When STOP signs are placed on all entering legs of an intersection, each STOP. sign may be supple- mented by a separate plate mounted below it with the message "3-WAY", "4-WAY', etc. The supple- mental plateshall have white letters on a red back- ground. Location: Erect in the standard position on the right or left at or near the eotranee to an intersection or at any location necessary to control traffic within an intersection.