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N Zf �l (n t7 " 0 n �g tt O (n o m O H tt x rt m m�J H F- :J �J O r• r• rt O F m 0 H rt '-d C 0 H o m m td FJ• o w m F- rh UI O (n 'd m rt m p (n Qq rh H H. m w (n r• tt r•op C °rt b 0 (n Qq Fl 0 QIl mq w Q�q w rwt O (D a Fn C-) H. rt C) 0 r• H m m rt aq t7 w rt m 0 rt 0 cr m Ft N H 110 00 00 14 IA M w z z H ''L The traffic volume warrants used for Dublin for all-way STOP sign control specify that the total volume entering the intersection from all. approaches must average 300 vehicles per hour (VPH) for any eight hours of an average day, and the volume from the minor street must average at ;least 1/3 of the total intersection volume (100 VPH minimum) . The approach volumes at the intersection of Silvergate Drive and Rolling Hills Drive average 188 VPH for the heaviest eight hours. The minor streets average :20% of the total volume and only 38% of the minimum volume warrant. Therefore, the minimum volume warrants are not satisfied by the existing traffic volumes. With the addition of 52 single-family homes yet to be built or occupied on Rolling Hills Drive, plus 80 homes to be built or occupied that would probably use Creekside Drive to access Silvergate Drive, there would be an estimated 258 VPH entering the intersection for eight hours, and the minor streets would-average 58 VPH. The minimum volume warrants for total intersection volume would be 86% satisfied, and the minor street volume warrant would be 58% satisfied. Accidents There were no accidents at this intersection in 1985, one each in 1986 and 1987, and none thus far in 1988. The accidents that occurred in 1986 and 1987 were not of the type related to intersection design and were not susceptible of correction by installation of STOP signs. Sight Distance and Critical Speeds The 85th percentile speed for north- and southbound traffic on Silvergate Drive south of Winding Trail was 39 MPH. TJKM feels that speeds near Rolling Hills Drive may be somewhat lower due to the uphill grades at the inLe section; _._._ Sight distance was measured for both the westbound and eastbound movements. Cars at the eastbound approach of Rolling Hills Drive can see virtually unobstructed to the south and for approximately 365 feet to the north. Cars at the westbound approach of Rolling Hills Circle can see for approximately 335 feet to the north. However, sight distance to the south is obstructed by the grade, the existing electrolier, and the newspaper vending machines on the corner. Also, if cars were parked on Silvergate Drive in the first 125 feet south of Rolling Hills Circle, the sight distance would be further restricted. Depending upon how far a car edges into the intersection, the height of oncoming cars, and debris in the landscaping, one could see up to 300 feet to the south. However, if a westbound vehicle pulls slightly over the existing brick pavement that crosses Rolling Hills Circle in lieu of a standard limit line, one can see clearly for only approximately 235 feet to the south. The presence of the newspaper racks causes a driver to peer around them and makes one feel that the sight distance is even more restricted than it actually is. The minimum stopping distance on wet pavement for vehicles traveling 39 MPH is 315 feet. This distance is provided clearly in both directions for eastbound traffic, but only in one direction (to the north) for westbound traffic. TJKM states that the sight distance for westbound traffic to the south could be improved by relocating the newspaper racks, requiring that the landscaping on the east side of Silvergate Drive be no higher than four inches (retaining the existing saplings as long as they continue to not obstruct visibility) , requiring that no debris be allowed to remain in the landscaping, and prohibiting parking for the first 125 feet south of Rolling Hills Circle on the east side of Silvergate Drive. The sight distance for a vehicle on Silvergate Drive desiring to turn left onto Rolling Hills Drive to opposing traffic is also a critical issue. A northbound or southbound vehicle has restricted visibility to the opposing traffic due to the crest vertical curve. The required sight distance is adequate if the approaching vehicle slows to 5 - 15 MPH. This is the prudent and legal way to make a left turn. However, if the driver of the vehicle starts the turn at a higher rate of speed, the situation changes. A driver approaching at 39 MPH would require a sight distance of 630 feet (i.e. , when -2- the driver is himself 315 feet from the intersection, he should be able to see a vehicle that is 315 feet on the opposite side of the intersection) . This sight distance is not provided for either north- or southbound traffic. Analysis and Recommendations While the minimum traffic volume warrants for all-way STOP signs for this intersection have not been satisfied, sight distance conditions, especially for drivers on Silvergate Drive turning left onto Rolling Hills Drive or Rolling Hills Circle, are such that TJKM does recommend installation of STOP signs at this intersection. The following are also recommended: 1) That parking be prohibited for 125 feet south of Rolling Hills Circle on the east side of Silvergate Drive. This area is adjacent to the townhouses only, and there is no residential frontage. 2) That the suggestion be made to the Townhouses Homeowners' Association that the landscaping be monitored to ensure clear visibility for drivers exiting Rolling Hills Circle, and also that the newspaper racks be moved if at all possible. (Staff has already addressed letters embodying these requests to the Homeowners' Association and to the newspaper companies.) Staff recommends that the City Council conduct a public hearing and adopt the resolutions. -3- RESOLUTION NO. -88 A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF DUBLIN DESIGNATING PLACEMENT OF STOP SIGNS ON SILVERGATE DRIVE AT THE INTERSECTION OF ROLLING HILLS DRIVE/ROLLING HILLS CIRCLE Pursuant to the provisions of Chapter 1, Section 5 of City of Dublin Ordinance 55-87, the City Council of the City of Dublin does RESOLVE as follows: Section 1. STOP signs shall be erected on Silvergate Drive at the intersection of Rolling Hills Drive/Rolling Hills Circle. Section 2. The provisions of Section 1 shall be added to Chapter 3 of the City of Dublin Traffic Code. PASSED, APPROVED, AND ADOPTED this 24th day of October, 1988. AYES: NOES: ABSENT: Mayor ATTEST: City Clerk RESOLUTION NO. -88 A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF DUBLIN DESIGNATING A NO PARKING ZONE ON A PORTION OF SILVERGATE DRIVE SOUTH OF ROLLING HILLS CIRCLE Pursuant to the provisions of Article 4, Section 23, of City of Dublin Ordinance 55-87, the City Council of the City of Dublin does RESOLVE as follows: Section 1. In the interest of public safety, parking shall be prohibited on Silvergate Drive at the following location: On the easterly curbline of Silvergate Drive, from the southerly curbline of Rolling Hills Circle, southerly a distance of 125 feet. -:_T._ -Section-2—.-=ha--provis-i-ons-°-of S ci-i-orr- shall bra-added-to--Chapter—_ -6 of the City of Dublin Traffic Code. PASSED, APPROVED, AND ADOPTED this 24th day of October, 1988. AYES: NOES: ABSENT: Mayor ATTEST: City Clerk COMMUNITY - SSOCIATIONS ' CONSULTING 6379 CLARK AVE. SUITE 200 DUBLIN, CA. 94568 (415) 833-0100 August 16, 1988 Mr. Lee Thompson, Director Department of Public Works City of Dublin 6500 Dublin Boulevard, Suite D Dublin, CA 94568 RE: Silvergate Highlands Townhouses Owners ' Association Tract 5410 Dear. Mr. Thompson, We are submitting this request to your office on behalf of the Silvergate Highlands Townhouses Owners ' Association at the request of The residents of this community are requesting two (2) additional "Stop" signs be installed at the intersection of Silvergate Drive and Rolling Hills Drive/Rolling Hills Circle. The signs requested would be located on Silvergate Drive, stopping the northbound and southbound traffic. These signs are requested to increase pedestrian safety across Silvergate Drive. More specifically, this is a community association with two (2) common areas designed for use by all residents. Common Area Parcel A, located at the east end of the property, contains a large grass area with barbeques and picnic tables for family activities. Common Area Parcel B, which is located on the west side of the property, includes the community swimming pool . Both areas are noted on the attached map. The residents enjoy the use of both areas and many travel back and forth across Silvergate in order to reach them. The homeowners are requesting the additional signs to reduce the speed on Silvergate Drive through their community and increase safety for themselves and their children. We thank you in advance for your consideration of this matter. If I can assist you in any way, please do not hesitate to contact me. Sincerely, %&26m ' ra A. 1%arren Association Manager cc: Chron. — Mgrs. Report Association File RECEIVED President' s File AUG 23 PUBLIC WORKS •.i. i e , . . .,.......„............../g;:•.X.:-::::',...:',": ar .y . 1 A 1 TRACT 5410 A % NOTE: A":v48 I1 INf OIRIl1f 1I WI IIININ f W fla f ; 10,f 4943 IOItrINtDf OF MIX, NAP Of M SVIJ(CI IOAV COT 01 DUBLIN AND UNINCORPORATED TERRITORY •� ��1,•?..._•�4�> 1R J torNIINtb US(rtrl 0/ R(COND IO f1DS, IN !NE COUNIT OF ALAMEDA. CAL!FORM! . COr7IT.,Warm IM LOOK 1776 Of O0A C, '•"�i/�Yvf II•I�i p G��1� . ....\":"\-:,,,, 7AGE )0,Warm/ /MOWS O/.AIIX[D/ COUMIr. o- .4,,,y• of'? L,1 I.� J� • 0�. /") JUNE 1986 SCALE I'•100' • c 'Kir C 't•!0 3011 Of,-' I It'.' '\\\\T+/] FCRCVSON G VOLIMAN :ONSULIINC ENCINEERS.1IN . /A p ` ril ee 0e' f2.,,Of., , 71 IN[ INItf 10R COV/f(! IMO IISIIMCIS FOR /JfCtlf PLEASANT, MILL. p.? ®® � •1141. A Art I Alf :NOS( SNOrr ON STMT A IXIDUCM /d, J' ® CC ;/•o7V°QS - II, IrClfJl1[ /Df lift IrrUlOf /OVND1Rl lIX(f I. L.5073'•DI Mr [Ilfitf Of Mt Smug Ir(1(ON. Dr , I®® Y o Z. < ' ") Arr ,/IF • . . . ' �© .„.,-s SITE `' 4 �:; Et47 ''1 `T 1r5 � ip% �o\��V 11A M /_ c // S ^ 10 tip Se . 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SS£: 72,4;: r s[wGVt.� . s = S O.. S7MM DEA.YE••S[K. i v'rs �q 4 � �<� �� 1�}O� � o�r;� wl�sos10 ��� IIw.E. Ar.�.•rcvi•rl.kzlstFw31 1.1+16 o..R.+.1 ••• .:-• e. �� zl 0?•C R•6df.00' CIJRV(ANA T)7AFAON NCAA ,� �'� u w li•FIp7✓ •a1 r'j4 j r� IR 5003 1•146.61.00. �; 0 C BASIS OF BEARINGS sr \� o+\1a+C°:06°, `I. % 6•>•30[/'t,1748 •ON ixt tONVW(rr tun' o� Snr(ltfr( port w/ IF KcvclZ ia '$ . �w WIN If Y I)'If'31 ' AS SNOIr OR IN( ��,My,•:;k��1 ,•,yi7•A1'x►'E • .p� tiv NAP Of SYI01 YIf10R If/CI 3001 fll/ Y 08I . /� i ,�.�t{; 'A:J•.'0' » AIJa•/'� `1 b _ \� dll•' ' ! ►�,10 b SlffEl 07// SME[i� Et 1601 • J , I,•? 1 . • - 51 P C V E E) MEMORANDUM P LiC Vir ;:S DATE: October 13, 1988 TO: Lee Thompson FROM: Michelle DeRobertis SUBJECT: Request for STOP Signs at Silvergate Drive and Rolling Hills Drive At your request, we have conducted a study of the need for all-way STOP sign control at the intersection of Silvergate Drive and Roiling Hills Drive. The study consisted of a field survey, approach volume counts, analysis of future development that would use Rolling Hills and increase existing traffic volumes, analysis of safe stopping distance based on a recent speed survey, and a review of accident history. Field-far-�e-y Silvergate Drive near Rolling Hills Drive is a two lane road with wide bike and parking lanes, and left-turn pockets for both northbound and southbound traffic on Silvergate Drive. The west leg of the intersection is Rolling Hills Drive, a two lane road with residential frontage. The east Ieg is the private road, Rolling Hills Circle, which also has residential frontage. Both the east and the west leg are controlled by STOP signs. Traffic Volumes Daily traffic volumes were counted at the four approaches to this intersection on September 22-23, 19S8. Silvergate Drive has the heaviest approach traffic�volumes: 1,009 vehicles per day (vpd) southbound and 949 vpd northbound. The west leg of Rolling Hills Drive has 473 vpd eastbound, and the east leg has 72 vpd westbound. The traffic volume warrants used for Dublin for ail-way STOP sign control specify that the total volume entering the intersection from all approaches must average 300 vehicles per hour for any ge eight hours of an average,. day, and the volume entering from the minor street must average at least one-third of the total intersection volume, 100 vehicles per hour (vph) minimum. (It should be noted that this volume warrant is 60 percent of the volume warrant as specified in the Caltrans Traffic Manual, and are therefore considered fairly liberal warrants.) The approach volumes at the intersection of Silvergate Drive and Rolling Hills Drive average 1SS vph for the heaviest eight hours, which is only 63 percent of the volume warrant, In addition, the minor streets avera`e 20 percent of the total volume, and is only 3S percent of the minimum volume warrant. Therefore, the existing traffic volumes do not satisfy the minimum volume warrants for all-way STOP sign control. Fifty-two single-fatuity homes have yet to be built or occupied on Rolling Hills Drive. In addition, another SO homes are to be built and occupied that would use Crceksidc to access Silvergate Drive. The traffic that would be generated by these homes was added to the existing traffic volumes to whether this additional 4037 Chabot Drive, Suite 214, Pleasanton,California 94566-(415)463-611 PLEASA\T..N•;AC .WENTO•FRESNO•CC.\ro a • Lee Thompson -2- . • - -October 13, 1988 traffic would cause the warrants to be met. It is estimated that after these homes • are occupied, there would be an average of 258 vph entering the intersection for eight hours and 58 vph would be on the minor streets (22 percent of the total intersection volume). Thus, the minimum volume warrants for total intersection volume would be 86 percent satisfied, and the minor street volume warrant would be 58 percent satisfied. Accidents The accident history at the intersection of Silvergate Drive at Rolling Hills Drive for the past three and one-half years was reviewed. There were no accidents in 1985, and one accident in each of 1986 and 1987, and none as of September 25, 1988. The accident in 1986 involved a single vehicle travelling southbound at approximately 45-55 miles per hour who hit the curb when attempting to turn onto Rolling Hills Drive. The accident in 1987 involved a car which hit a parked car when backing on Rolling Hills Circle. The primary cause of these accidents is unrelated to the intersection design, and neither of these accidents are susceptible • of correction by STOP sign control. Sight Distance and Critical Speeds o-rr e Dave so-utlr- d ng `Trails"w"e-re-surveyCC! on'"� ^` March 17, 1988. The 85th percentile, or critical, speed for southbound and northbound traffic was 39 miles per hour. At Rolling Hills Drive, the speeds are probably slightly lower due to the uphill grades at the intersection. The sight distance was measured for both the westbound and the eastbound movements. Cars at the eastbound approach of Rolling Hills Drive can see virtually unobstructed to the south and for approximately 365 feet to the north. Cars at the westbound approach of Rolling Hills Circle can see for approximately 335 feet to the north. However, the sight distance to the south is obstructed by the grade, the existing electrolier and the newspaper vending machines on the corner. Also, if cars were parked on Silvergate Drive in the first 125 feet south of Rolling Hills Circle, the sight distance would be further restricted. Depending on how far a car edges into the intersection, the height of oncoming cars, and debris in the landscaping, one could see up to 300 feet to the south. However, if a westbound vehicle pulls sightly over the existing brick pavement that crosses Rolling Hills Circle in lieu of a standard limit line, one can see clearly for only approximately 235 feet to the south. The presence of the newspaper racks causes a driver to peer around them and makes one feel that the sight distance is even more restricted than it is. The minimum stopping sight distance on wet pavement for vehicles travelling 39 mph is 315 feet. This distance is provided clearly in both directions for eastbound traffic but only in one direction, to the north, for westbound traffic. The sight distance for westbound traffic to the south could be improved by relocating the newspaper racks either further to the east on the present corner or to the west side of Silvergate Drive, requiring that the landscaping on the east side of Silvergate Drive be no higher than four inches, retaining the existing saplings as long as they remain at their present condition of not obstructing visibility through them, require that no debris be allowed to remain in the landscaping, and prohibiting parking for the first 125 feet south of Rolling Hills Circle on the east side of Silvergate Drive. t /`rj >+µ r,;j r,1✓ r✓1:+ 7 _ .PW� y/ Vii.. + i r» f u '.-t }r l 'r _ r - .i .�..'J do-tt�rc'/ a a {r;,, ✓x .i'; !r+ f .,r /, ✓�, J, t'. � hr���• y ,r,j,+ -✓ Y. � i t - � st t L,y - r f .✓ ✓- :r < 2.;. n - r i i - S s' f�✓ ,j 1 ,a'. 4 , +J�+i t 4 ✓ t<l. {,�• �titt.'orri-�Gjl o:.i s :. < %yr�' .>tsl+ ,i� !/ry<.�( S'f`i.�i �r / ^aria °L't'" r�,.�'�+.t -�/.� !a�+-a i .l .. ty,. � .ua+,>(r� d' � A..'YY 9't i,! Yf: I �,r G��_ n(1 - ��i'� [ P' l a ��`•� t 7a ' ✓ �'L♦ y ; •,+.rnt •:e.:�;a.,,'.?l„rY�o.��t'yu'.f y-,,J..fiJ`r1 A'r✓�r� r T�hoj)J��3m 4 14 .i•4„.,yr n 7-Z'✓s r t^,t�i4 druY,4r 3 r S r f x v�}J V� +j Y sf i�=.Hr MI l=�s'r 6 F,�r rur Y O.:�cdfr yr,lb,—r y 9r:s 8f.C8 , _• j,i�!✓ . r �.vr -��' v'••7y. C��y,-�-1 iw� f}. -t rp.'-tr7. �� I,. � r .n...i�y •iry{. �+sib-. ::� - 4f.� v j4 ,-LT it �•{.�'.•rC5-..1.:C - ' »s d ;Thesight-distance fora vehicle'on Silvergate D rive desiring Jto£turn=left.:onto ' Rolling'Hills Drive to"Ropposineiraffic-Tis also Ciiticif issue A northbound or ? ; southbound vehicle has restricted visibility to the opposing traffic due to the crest vertical curve. The required sight distance is adequate if the left turning vehicle slows to 5-15 miles per hour to ascertain if there is no opposing traffic before making a decision to turn left. This is the prudent and legal way to execute a left- turn. However, if the driver of the vehicle intends to start the left-turn traveling at a higher speed, then the situation changes. A vehicle traveling at the 85th percentile speed of 39 miles per hour would require a sight distance of approximately 630 feet, i.e., when a vehicle is 315 feet from the intersection (the stopping sight distance for a vehicle traveling 39 miles per hour), the driver of the vehicle should be able to see a vehicle 315 feet on the opposite side of the intersection. This sight distance is not provided either for southbound traffic or northbound traffic. Analysis and Recommendations The existing traffic volumes are only 63 percent of the minimum volume warrants, and the minor street volumes are only 38 percent of the minimum volume warrants. After.the build-out of the approved units with access to Rolling Hills Drive and Creekside Drive, the minimum volume warrants for total intersection volumes a� ld ie "praxima-rely T87_-_p erceat._ ed --a-nd--t_h-e_-min-or---street-v-olume------ --___.__..------__---- warrants would be 58 percent satisfied. Thus, STOP signs are not recommended -based on the minimum volume warrants. If STOP signs are installed when minimum volume warrants are not met and there are no other conditions present which warrant all-way STOP signs, then motorists tend to come to rolling stops rather than complete stops. In addition, if side street traffic is not a significant portion of the total intersection traffic, cars on the major street tend not to look out for cars on the side street. Therefore, all-way STOP signs that do not meet minimum volume warrants are not advisable. At the intersection of Silvergate Drive and Rolling Hills Drive, there is adequate sight distance in three of the four critical directions. In the fourth direction, looking southerly for westbound traffic, clear sight distance exists for only 235 feet. The safe stopping sight distance is 315 feet, based on a critical approach speed of 39 miles per hour. The sight distance at this approach can be improved to approximately 310 feet by restricting parking for 125 feet on the east side of Silvergate Drive, maintaining the landscaping so that it does not impair visibility (see previous section), and relocating the newspaper racks to the west side of Silvergate Drive or further to the east at their present location. However, these measures will not improve the sight distance for either northbound or southbound left turning traffic. If left turning traffic prepares to stop before executing their turn, as is legal and prudent, the sight distance is adequate. However, if a driver does not prepare to stop, the sight distance is not adequate. In summary, sight distance restrictions do exist, the existing volumes satisfy the total intersection minimum volume warrant, and the minimum volume warrants for side street traffic are 58 percent satisfied. Therefore, it is recommended that all-way STOP signs be installed at the intersection of Silvergate Drive at Rolling Hill Drive. rhm 157-OO1M.3MD • • C n .. . • , . . � o ( � . , Q � � . . CO 1i COL 4,NG ,, i J • . D,q/►iE " I II / R1 . d . . BRICK PAVED . C-• 1LLK ftft....***7 ' . . __ R1 )1 ::::":Igig - 11[1i . , , . ;::t:3::::::: ME- . ' i 1 er . I I I • I ':: CITY OF DUBLIN . EXISTING CONDITIONS - w FIGURE INTERSECTION OF , ;: 4.,,: . y 1 . SILVERGATE DR. & ROLLING HILLS DR. • .• TRANSPORTATION CONSULTANTS • 0 INSTALL / ` WI7 8W17.A T / / LEGEND . b EX. SIGN / / / z cir EX. STRIPING ,J Ct t , N NEW SIGN O 4/ : f NEW STRIPING k . Q I s v INSTALL RI ' '40LL/NG H/LLS �� la..._. �R/VE I ( r -a- d01S .;,1 :,' d BRICK PAVED INSTALL C". . LK 12" LIMIT LINE T o & ,.STOP` L RI 1**"."*".47 , 9 LEGEND • M . STOP STOP • ::IL-- w ::cfl::: Z ::a: J <.. J - REMOVE ALL CONFLICTING a MARKINGS - REPAINT a STOP LEGENDS IF NECESSARY I ��INSTALL WI7 & WI7A CITY OF DUBLIN . - - STOP SIGN INSTALLATION FIGURE INTERSECTION OF SILVERGATE DR. & ROLLING HILLS DR. • , 4441 - 2 'TRANSPORTATION CONSULTANTS