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HomeMy WebLinkAboutHMP 15-01; ADAMS STREET GUARD RAIL DETERMINATION; 2018-10-19SOWARDS AND flOWN ENGINEER G, INC. 43to.) /oftb/,g. October 1, 2018 LREE RD COPY Cityof Carlsbad 1635 Faraday Thte Carlsbad, CA 92008 Re: Adams Street Guard Rail Determination - GR 2018-0019 (APN: 206-200-03) A portion of Adams Street is to be widened as a part of a proposed grading plan for a single family residence on a currently vacant site. The site resides one lot East of 4465 Adams Street and two lots West of 4485 Adams Street. The road has already been widened in front of 4485 Adams Street and pervious parking is installed in front of 4465 Adams Street. This letter is to address whether a temporary barrier at the East end of the road widening should be a guard rail, a wood post barricade, or no barrier at all. The site in question is rectangular with a roughly 4:1 slope descending South from Adams Street to the Agua Hedionda Lagoon. There is gravel parking South of the Adams Street pavement, 8.5' wide and roughly 65' above the lagoon. The roadway will be widened 10 feet South of the existing edge of pavement as a part of the proposed grading plan. The West edge of the widening will abut the pervious parking on the lot to the West. The East edge of the paving will be narrowed back to the existing edge of pavement and a temporary slope will be added to transition from the new road grades to the existing dirt grades. The temporary barrier will be placed along the Easterly transition at the top of the temporary slope. Per the City of Carlsbad Engineering Department, the governing document for guard rail determination is a Caltrans document "Traffic Safety Systems Guidance". Pages 16 through 18 of this document will be added to this letter as a reference. Section 3.3 of this document gives 5 criteria to be considered when installing guard rails. In addition, section 3.4 gives additional criteria to consider when the guard rail is at the top of an embankment slope. Each of these criteria will be accessed below as an aid in determining whether a guard rail is appropriate for this application. Collision History: The Carlsbad Police Department was contacted to see if there is a history of cars leaving the roadway at this location. Unfortunately no information was obtained as of this date and we have no information to make an assessment of this criteria. Roadway Alignment: Adams Street curves in front of the site, and is sharply banked to the North. The curve ends just East of the site and the road continues another 400' Easterly before sharply turning and continuing North. Looking Westerly, the road curve continues West and North 500' to a stop sign intersection with Highland Drive. The above factors, plus offsite parking and several driveways along the east-west portion of the road force drivers to proceed slowly along this section of road. 2187 NEWCASTLE AVENUE • SUITE 103 • CARDIFF BY THE SEA, CA 92007 (760) 436-8500 • FAX (760) 436-8603 3. Operating Conditions: There are three sections to this criteria which will be addressed individually: Volume: Adams Street is a two lane road and traffic volume is light in this region. Speed of Traffic: The posted speed limit on Adams Street is 25 mph, while the sharp curve to the East has a posted speed limit of 15 mph. The alignment discussed above makes it difficult to drive in excess of the speed limit, reducing the possibility of drivers leaving the roadway. Merge and Weave Areas: Adams Street continues as a two lane road throughout this area of discussion. There is off-street parking and driveways on both sides of the road which may cause collision avoidance maneuvers. In conclusion, the light traffic volume and low, traffic speeds reduce the probability of run-off-road collisions, whereas the off-street parking and driveways increase the possibility. 4. Climate Conditions: With the exception of potential morning fog, climate is not a factor in this determination. 5. Roadside Recovery Area: Roughly 75 feet of roadway will be widened in front of the site and the East transition will extend another 30 feet in front of the adjacent 75' wide lot to the East. The transition length of 30 feet is sufficient to minimize the risk of an accident. Section 3.4 Guardrail at Embankment Slopes: The purpose of this section is to evaluate whether a collision with a guard rail is more severe than rolling down the embankment slope in accordance with attached Figure 2. As stated earlier, the slope descends from the gravel shoulder 65 feet at a 4:1 slope to the waters of the Agua Hedionda Lagoon. Per Figure 2, all 4:1 slopes are less damaging than the guard rail, therefore a guard rail is not recommended. There are factors discussed above which suggest the need for a barrier at the subject location. As the likelihood of a run-off-road accident is low, we feel a barricade is appropriate for this application. We propose the use of a guard post barrier per SDRSD M-09 as reasonable design for this application. andy Bro RCE 36190 SAFETY SYSTEMS GUULNCE 16 7-2017 and Type 60GB. With the adoption of the MASH standards the use of Type 60S series is no longer allowed and must not be used. See the Structures XS Sheets for additional details for structure columns and sign pedestals enclosed by Type 60R and Type 60SD series bathers. For more information about these de- tails go to the Structures XS Sheet site at: http://www.dot.ca.gov/hg/esc/tech- pubs/manual/bridgemanuals/bridge-standard- detail-sheets! Note that the details on the Structures XS Sheets are non-standard and require an excep- tion to be used (See Appendix A). Proposed appurtenances on concrete guardrail, except Standard Plans details, must be approved by the District Traffic Safety En- gineer and documented in the project files. 3. Cable Guardrail is a high-tension three or four- strand flexible bather. It may be recommended by the District Traffic Safety Systems Coordi- nator for locations that can accommodate cable deflections up to 9.5 feet. See Topic 4.6(3) for details on cable barrier. Cable guardrail must be approved by the Headquarters Traffic Operations Liaison and the Deputy District Directors for Traffic Oper- ations and Maintenance. Documentation of the approval must be placed in the project files. 3.3 Guardrail Installation Criteria When considering installation of guardrail at an embankment or a fixed object the following criteria, although not an all-inclusive list, may be used as a guide: 1. Collision History: Based upon the run-off-road coffision history, statistical experience or anal- ysis can be used to evaluate if guardrail is needed. 2. Roadway Alignment: Isolated curves on rela- tively straight roadway alignment may increase the risk of running off road. Also, on roads with curving alignment, curves that are sharper than expected may increase the probability for run- off-road collisions. 3. Operating Conditions: The location's traffic characteristics can also affect the potential for a vehicle to leave the traveled way: Volume: The higher the volume of traffic, the greater the potential for run-off-road collisions. Speed of Traffic: Higher operating speed can increase the potential for run-off-road collisions, and will affect the distance that a vehicle will traverse before the driver can regain control or bring the vehicle to a stop. Merge and Weave Areas: The potential for run-off-road or lane departure collisions may increase in the vicinity of ramp merge and diverge areas, especially those without auxiliary lanes where stopped or slowing traffic can cause abrupt lane changing and collision avoidance maneuvers. 4. Climate Conditions: Frequent dense fog, rain, or snow and ice conditions increase the risk of run-off-road collisions. 5. Roadside Recovery Area: The risk of a run-off- road vehicle colliding with an embankment or a fixed object is greater as the recovery area de- creases. The highway facility type, whether a freeway, expressway, or a conventional highway, has an im- pact on the analysis for installing guardrail due to the differing characteristics of these facilities. For example, the presence of driveways may prevent the 'installation of guardrail to shield an object within the CR2. Funding limitations and differing operating conditions preclude firm rules for in- stalling guardrail. 3.4 Guardrail at Embankment Slopes Installing guardrail to shield embankment slopes is largely a result of analyzing the above cri- teria on a case by case basis and determining whether a vehicle hitting guardrail is more severe than going over an embankment slope. A tool de- veloped for evaluating this severity, the "Equal Se- verity Curve" (see Figure 2), developed in the 1960s and updated in the early 1980s, is still appli- cable. The line in Figure 2 represents collisions at combinations of embankment height and slope that resulted in seventies generally equal to the severity of an average guardrail collision. If combinations of embankment height and slope plot close to the line, the severity of an errant vehicle going over an em- bankment may be greater or less than the severity SAFETY SYSTEMS GUINCE 17 of striking the guardrail, so the shaded areas of the line should be regarded as a band. When the site specific embankment height and slope conditions plot above the equal severity band, the severity of colliding with the guardrail should be less than the severity of a run-off-road vehicle going over the embankment. Therefore, guardrail can be installed when the embankment height and slope plot above the band, and the criteria in Topic 3.3 are consid- ered. Although an embankment slope may not qual- ify for installation of guardrail based on application of Figure 2, the presence of fixed objects along the slope or bodies of water, school grounds, or other fixed objects at the toe of slope or beyond the CRZ, can justify guardrail at such locations. For this rea- son local site conditions need to be considered in conjunction with Figure 2. Guardrail placed to shield an embankment slope should shield both directions when the em- bankment is within the CRZ for each direction of travel. See Figure 3. For more information on clear recovery zones on conventional highways see Topic 2. The District Traffic Safety Engineer must con- cur with the decision to install or not to install guardrail and the type of end treatment at an em- bankment slope that meets the "Guardrail Less Se- vere" conditions of Figure 2. The statement of con- currence must be documented in the project files (see Topic 1.3 for guidance). Copies of the Typical Cross Sections, Sum- mary of Quantities and applicable Layout sheets from the Project Plans may supplement the docu- mented statement of concurrence inserted in the project files. 3.5 Guardrail at Fixed Objects Guardrail should be considered at all fixed ob- jects that are accessible to traffic and within the CRZ, whether to the left or right of traffic. Guard- rail may also be considered at fixed objects located 7-2017 beyond the CRZ when such objects occupy an oth- erwise clear recovery area. MGS with standard post size and spacing will be placed as far as possible from the edge of pave- ment, where the slope is 10:1 or flatter, but no closer than 36 inches from the back of the post to the face of the fixed object. This clearance between the guardrail and the fixed object is necessary since guardrail deflects up to 36 inches during impact. Guardrail that is to be installed less than 36 in from back of post to the face of a fixed object but not less than 12 inches from back of post to face of fixed object shall be constructed according to "Strengthened Railing Sections for Fixed Object" detail of the Standard Plans. See Topic 3.6(10)(c) for discussion of this detail. If guardrail is to be installed less than 12 inches from the back of post to face of fixed object, concrete barrier must be used. See Topic 3.2 for allowable types of concrete bather to be used as guardrail. Where there is a row of structure columns with less than 26 feet in-be- tween each column, the strengthened railing section detail should be continued between the columns. Where the column spacing exceeds 26 feet, a new detail may be started. Placement of guardrail, itself a fixed object, may also increase the probability of a vehicle col- liding with the guardrail. For this reason, fixed ob- jects such as individual signal poles, lighting stand- ards, utility poles, trees, or traffic control cabinets are typically not shielded by guardrail. Guardrail shall be placed at the following fixed objects within the CRZ that are not shielded by other traffic safety systems: Overhead sign posts, Structure piers, columns, and abutments, and Exposed ends of walls. See Standard Plans for additional details where walls are above the height of guardrail. > TRAFFIC SAFETY SYSTEMS GUINCE Figure 2: Equal Severity Curve 1:f GUARDRAIL LESS SEVERE LJLJJIL JVIiUi GUARDRAIL - MORE SEVERE 0 10 20 30 40 50 EMBANKMENT HEIGHT (FEET) 1:1 t5:1 2:1 3:1 4:1 18 7-2017 see note 1 see r Back of Sock of sidewalk sidewalk In n n 611-011 Top View max. see note 4—Joint (typical) 00 Co OD H I I ,.-Ground Line I I I II II II II II II II II II II ( II I! II II II I I I I I 6"x6" I I ii Front View *"post typ. I I I I I I I CONTINUOUS BARRICADE End View Location (Both dimension I shown on I 12"I I12"I plans cades)cades) 17-1 00 1 I: :lI[ I TGround [J Ground Line 00 CNI i Line II / H " 6"xB" post typ. II I I I •\ Co Co Ij I i I III4"x4" Ipost I Front View I III NOTES L...J SEPARATE BARRICADE L..J LfJ 1. Posts to be structural grade redwood or pressure treated (with wood preservative) Douglas Front View Fir, surfaced four sides; cross pieces to be 2"x8" select grade Douglas Fir. surfaced four sides. GUARD 2. All exposed portions of barricades shall be pointed with two coats of white exterior enamel over prime coat. POST 3. Connections shall be made with 3/8" x 6" galvanized lag screws with one (1) washer each. 4. Reflector sign fastners to be 3/8" x 1 1/2" galvanized lag screws. 5. Reflector signs - California Type N. Size 18" x 18" - Yellow with nine (9) 3 1/4" reflectors LEGEND ON PLANS (center mount). Reflectors shall be red for use on dead end streets, in all other cases they shall be yellow. Reflector material shall be plastic or other approved reflectorized material. Barricade Sign material shall be aluminum alloy 6061-16 or 5052—H38. aluminum thickness 0.063". 6. 6' long hot section metal post per Coltrans Std. Plan A74—A optional for guard post. Guard Post RECOMMENDED BY THE SAN DIEGO Revision By Approved - SAN DIEGO REGIONAL STANDARD DRAWING REGIONAL STANDARDS COMMITTEE TEXT Bus 2/11 REVISED 0. Gerchoffi 12/17/2O 15 GUARD POST AND BARRICADE Chdfrperson R.C.E. 19246 Dote DRAYINC NUMBER M-09