Manual Notice: 2020-1
From: Camille Thomason, P.E
Manual: Roadway Design Manual
Effective Date: July 01, 2020Anchor: #URCLQECD
The Roadway Design Manual has been revised to update roadway policy in accordance with FHWA guidelines and with comments received from Design Division, other Divisions, and TxDOT's 25 Districts. As a result, revisions were made to Chapters 1-8 and Appendices A, B and C. Also, new Appendices D, and E were added to the manual, that is, Right Turn Slip Lane Design Guidelines and Alternative Intersections and Interchanges, respectively. Likewise, minor errata type corrections and edits were made throughout the manual.Anchor: #RHVQSUWB
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- Revised Roadway Design Manual Format for chapters 7, 8, Appendix C, and to include the addition of Appendices D, and E. Anchor: #PLXLHDHK
- Under External Reference Documents, updated references.
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- Revised controlling criteria per FHWA guidance for Design Exceptions, Waivers, and Variances. Reduced controlling criteria from 13 to 10. Anchor: #ORCSTVND
- Under Design Exceptions, added guidance that 4' minimum width is required for new bike lanes. Widths less than 4' will require a design exception. Anchor: #AGAGELES
- Under Design Exceptions, added guidance that design exceptions for bridge rails shall be sent to Bridge Division. Anchor: #RJPHAOOS
- Under Design Waivers, removed "non-controlling criteria for the" from introductory sentence. Anchor: #EHJLIFXG
- Under Design Waivers, removed requirement for copy of documentation being furnished to Design Division. Anchor: #VRYBONHC
- Under Design Waivers, added "Shared Use Paths (if this is the chosen Bicycle/Ped facility)" to 4R. Anchor: #HBBRDIDC
- Under Special Facilities, moved sentence "Design waivers are not applicable…" to the bottom of the section. Anchor: #VQQOCTFX
- Revised Design Exceptions and Design Waivers for Bicycle Facilities. Anchor: #AMXYPFUU
- Revised section on Design Variances for design documentation for PROWAG. Anchor: #KMQFRSPF
- Under THFN, provided link to Design Division’s Roadway and Hydraulics website.
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- Revised entire section of Schematic Layouts to include additional items for proper review and evaluation. Anchor: #AJFGCHGC
- Added "Location of wildlife crossing structures" to list.
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- (IAJR) was revised to incorporate: FHWA Updated Policy on Access to the Interstate System, May 22, 2017 and Current TxDOT IAJR Policy Memo, October 2018. Anchor: #ISFQHLJT
- Removed reference to 23 CFR 630 and replaced it with reference to United States Code (USC)-Title 23 Section 111. Anchor: #GWNIKQAT
- Added reference to the TxDOT IAJR SOP.
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- Replaced the Preliminary Design Submission Table with a list of preliminary design processes that affect/influence decisions and a list of reference material for the various submittal processes.
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- Added verbiage for twin bridge structures providing 10' distance to facilitate access for inspections.
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- Under Speed, added guidance on "Speed, Design Speed, Operating Speed, Posted Speed, and Running Speed". Anchor: #XMIOKBCL
- Added guidance and discussion on "Terrain". Anchor: #XIVRTHKT
- Added content to emphasize Crash Data, Highway Safety and Safety Analysis. Anchor: #IVTPORBV
- Updated Table 2-2. Defined variable (t) as time in seconds.
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- Under Intersection Sight Distance, added guidance that intersections should be free of conflict points to the extent allowable to promote safety. Anchor: #ILGFUTFM
- Under Intersection Sight Distance, added reference to AASHTO for intersection control guidance. Anchor: #MHJIRBYF
- Added new Figure 2-1.
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- Updated Table 2-3. Changed title of table and changed footnote 2. Anchor: #PPIIIUJS
- Updated Table 2-4. Changed title of table and deleted footnote 1. Anchor: #IFMPOUEL
- Updated Table 2-6. Changed title of table. Anchor: #CNYPKBRO
- Updated Table 2-7. Changed title of table. Anchor: #UODUXBPB
- Specified that the calculated transition length, LCT, can be calculated using adjustment factors as shown in Table 2-9. Anchor: #KQAFPPYP
- Under Super Elevation Transition Type, specified that linear superelevation transition may be used.
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- Clarified that the "roadway" grade should seldom be less than 0.5 percent for unpaved ditches and 0.25 percent for lined channels. Anchor: #TRBVWDAR
- Combined content for Crest and Sag Vertical Curves into one section named "Vertical Curves". Anchor: #ULBULDAA
- Added guidance on Sag Vertical Curves discussing the 4 different criteria, light beam distance, and stopping site distance. Anchor: #JPORCJWA
- Replaced Figure 2-6. Anchor: #WDMCRMRF
- Replaced Figure 2-7.
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- Added cross slope guidance stating that the cross slope should not exceed 3 percent on a tangent alignment unless there are 3 or more lanes in one direction of travel. Anchor: #EWMDSKRI
- Under Pavement Cross Slope changed guidance for the algebraic difference of cross slope between the traveled way and the shoulder grades should not exceed 6 percent. (Previously 6 to 7 percent) Anchor: #DHWOSRRK
- Clarified the width of flush or curbed medians for pedestrian refuge is 6' from BOC to BOC preferred and 6' from FOC to FOC minimum. Anchor: #YFHNFRKL
- Under Medians, added content for Design Guidance to Reduce Consequences of Median Encroachments, Design Guidance to Reduce likelihood of Median Encroachments, and Countermeasures to Reduce Likelihood of Median Encroachments. Anchor: #EEYMHACA
- Guidance was added for bicycle accommodation for urban streets and rural projects. Anchor: #XIPUIJPG
- Guidance was added for measurement of shoulder widths on bridge structures. Anchor: #NJONBMGR
- Under Shoulder Widths, adjusted language and guidance for Shoulder Widths. Anchor: #HQRRNUOB
- A clarification was made for shoulder widths to accommodate bicycle facilities across bridges being replaced or rehabilitated to be 5' minimum unless it's on the off-system and less than 400 ADT. Anchor: #RSEJOYDX
- Under Sidewalk and Pedestrian Elements, requirements under PROWAG and TAS was added. Anchor: #FUHBVPTA
- Under Sidewalk Location, removed the guidance for roadways classified as rural, the shoulder may be used to accommodate pedestrian and bicycle traffic. Also, removed guidance for where a shoulder serves as part of the pedestrian access route, it must meet PROWAG requirements. Anchor: #IKBOPJIN
- Under Sidewalk Width, added guidance that where there is a 4' sidewalk for short distances, a 5' width is required just after a pedestrian ramp for wheel chair maneuverability. Anchor: #NKIGDQSQ
- Under Walking Speeds, added "or near schools" for a location of walking speed of 3.0 ft/s. Anchor: #XQRBUXWB
- Under Street Crossings, added guidance for when push buttons are required for crossings. Anchor: #PTGUEGKR
- Updated Figure 2-8. Changed Figure to black & white. Anchor: #VXPSFSLB
- Updated Figure 2-10. Changed Figure to black & white. Anchor: #WHYRCCQV
- Under Curb Ramps and Landings, changed "should" to "shall" for guidance on curb ramps and landings Anchor: #GBQIYTXR
- Under Curb Ramps and Landings, added "Curb inlets" to list of obstructions that should not be located within the curb ramp, maneuvering area, or landing. Anchor: #NUOQISKS
- Under Street Furniture, added guidance with PROWAG & TAS. Anchor: #XMGYXBJX
- Under Front Slope, added guidance for slopes greater than 1V:2.5H. Anchor: #WCUYJNLQ
- Under Clear Zone, deleted sentence "For fill slopes steeper than 1V:4H, errant vehicles have a reduced chance of recovery and the lateral extent of each roadside encroachment increases." Anchor: #NERIEKBY
- Table 2-12 was updated. Changed clear zone criteria for minimum and desirable for Rural Arterial.
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- Under Bridge Class Drainage Culverts, clarified language for bridge class culvert protection. Anchor: #MFJLKTTB
- Updated Table 2-14. Added verbiage to table under "Treatment". Anchor: #LIWJTINV
- Updated Table 2-14 to include Note to refer to Bridge Division for further guidance. Anchor: #EGTTOLQY
- Updated Figure 2-11. Changed "Note" on Figure. Anchor: #DEEQBQEQ
- Under Side Ditches, changed "horizontal clearance" to clear zone. Also, made this change for the entire RDM.
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- Clarified and expanded on requirements for a non-state intersecting roadway’s need to adapt its alignment to a TxDOT road. Also, added guidance for an intersecting road that is modified and changed to tie into a TxDOT facility due to the request of the county or city.
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- Table 3-1, Maximum Gradient link was corrected to Table 2-11. Anchor: #XOVGMDTL
- Table 3-1, footnote 11 was changed to "A 5' minimum clear space for bicycles should be provided on bridges being replaced or rehabilitated except on off-system facilities with less than 400 ADT." Anchor: #EYHCGBDV
- Table 3-1 footnote 12 was added giving guidance on vertical clearance requirements for roadways on the THFN. Anchor: #RTFYLHWS
- Under Raised Medians, guidance was added stating "A median width of 18' is required if pedestrian refuge area is needed, see Figure 2-10." Anchor: #DKJYFNCY
- Under Raised Medians, changed guidance to 6 feet for a pedestrian divider. Anchor: #UHADVJND
- Under Left-Turn Deceleration Lanes, guidance was added stating "Where pedestrians may be present, the divider must be a minimum of 6', see Figure 2-10." Anchor: #OKLPOTOM
- Updated Table 3-3. Changed footnote 5. Anchor: #GRCEFKDP
- Updated Table 3-4. Added more "Speeds" to the table. Anchor: #ISKWRVQR
- Added guidance for Right-Turn Acceleration Lanes stating "Acceleration lanes typically are not used on urban streets. See Section 5, Figure 3-10 for acceleration distances and taper lengths, if an acceleration lane may be necessary."
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- Updated Table 3-5. Added footnotes 7 & 8 to table and fixed reference links. Anchor: #GKYVBJTS
- Under Clear Zones, link for Clear Zones was corrected to Table 2-12.
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- Updated Table 3-6. Changed footnotes 1 & 2 and corrected superscripts on table. Anchor: #PSYJHQER
- Updated Table 3-7. Corrected footnote 2 and reference links. Anchor: #EKVYGRUC
- Updated Table 3-8. Added footnote 7 and corrected superscripts on table. Anchor: #CIMMSITU
- Updated Table 3-9. Footnote 1 was adjusted to add guidance on the Clear Width on bridge structures. Anchor: #AKEKNWRI
- Updated Table 3-10. Table was reformatted. Anchor: #XKRPPXXF
- Updated reference to Table 3-11. Anchor: #HXBJRWDY
- Under Left-Turn Deceleration Lanes, corrected table references stating "Lengths of left-turn deceleration lanes are provided in Table 3-11 for Two-Lane Highways and Table 3-13 for Multi-Lane Rural Highways." Anchor: #UXPILFJN
- Under Right-Turn Deceleration Lanes, added guidance stating "Where the right turn deceleration or acceleration lane is being constructed adjacent to the through lanes, the minimum land width is 10' with a 2' surfaced shoulder." Anchor: #JEQOOBWP
- Under Right-Turn Acceleration Lanes, corrected table reference to Table 3-3 for acceleration distances and taper lengths. Anchor: #JYMKOQOW
- Under Intersections, added guidance stating that "Desirably, the roadways should intersect at approximately right angles, and should not intersect less than 75 degrees. Where crossroad skew is flatter than 75 degrees to the highway, the crossroad should be re-aligned to provide for a near perpendicular crossing."
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- Table 3-12, for Design Speed (Arterials) changed footnote to 1. Anchor: #LVMYEGOC
- Table 3-12, added guidance for Vertical Clearance for new structures. Anchor: #JACQKFCB
- Table 3-12, footnotes 2 & 3 clarified what heavy betterment and unusual circumstances means. Anchor: #MFMKTJER
- Table 3-12, added footnote 5 for guidance on roadways on the THFN. Anchor: #XRWLWNJW
- Table 3-12, added footnote 6 for design guidance on vertical clearance. Anchor: #LSXXQSRW
- Table 3-12, re-wrote footnotes 2 & 3 to include "documented through design exception" and deleted example. Anchor: #OFQDGJHG
- Table 3-12, changed "flat" to "level". Anchor: #JCBYSXQR
- Table 3-12, added 3 columns of 12' for Lane Width. Updated Metric. Anchor: #WJGWKRXM
- Table 3-12, clarified language for bridge clear width in footnote 7. Anchor: #PVMHSABY
- Under Four-Lane Undivided Highways, revised paragraph for better understanding of previous verbiage of "betterment projects". Anchor: #WFMXQGVW
- Corrected link to Figure 2-2, Determination of Length of Superelevation Transition. Anchor: #RMKLQJXY
- Corrected link to Table 2-11, Maximum Grades. Anchor: #TFYKLYBP
- Corrected link to Table 8-11, Earth Fill Slope Rates. Anchor: #RJPIOCIT
- Updated Table 3-14. Table was reformatted.
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- Table 3-15, corrected links to Clear Zone Table 2-12 and Maximum Grades Table 2-11. Anchor: #UWSUSPLI
- Table 3-15, added row for Lane and Shoulder Widths. Anchor: #YHLEBKOP
- Under Level of Service, added guidance for other Measure of Effectiveness (MOE’s) may include travel time, speed and queue lengths in heavily congested areas. Anchor: #MMKBXWSO
- Under Lane Width and Number, corrected reference to Figure 3-15, Typical Freeway Sections. Anchor: #NCVJILHN
- Under Shoulders, corrected reference to Figure 3-15, Typical Freeway Sections. Anchor: #LTOIXIRY
- Under Medians, corrected reference to Figure 3-15, Typical Freeway Sections. Anchor: #DKAUDEKG
- Under Vertical and Clear Zone at Structures, added guidance for roadways on the THFN. Anchor: #BXGFVABL
- Under Vertical and Clear Zone at Structures, added guidance to refer to specific railroad company guidelines for additional vertical clearance requirements. Anchor: #WOGXXGAX
- Under Vertical and Clear Zone at Structures, added railroad guidance. Anchor: #SWHFUALE
- Under Vertical and Clear Zone at Structures, removed sentence on the exceedance of 3 inches which was obsolete due to the requirements of the THFN. Anchor: #IYREMTGK
- Removed Figure 3-16, Typical Highway Railway Overpass and all its references. Anchor: #COPEYOOW
- Under Horizontal, corrected link to Table 2-12, Clear Zones. Anchor: #AAKEUMLL
- Updated Table 3-18. Corrected superscripts on table. Anchor: #SHUOJNDH
- Under Frontage Road Design Criteria, corrected link to Table 2-12, Clear Zones. Anchor: #ETUHNMGB
- Updated Table 3-19. Table was reformatted. Anchor: #KIRPJMAE
- Under Design Speed, added guidance for design speed for where a ramp joins a frontage road. Anchor: #VHITXNSB
- Under Horizontal Geometrics, corrected links to Figures 3-28, 3-29, 3-30, 3-31, 3-32, 3-33, and 3-34. Anchor: #VABOTRJU
- Updated Figure 3-36. Changed weaving distance to be from nose of gore to nose of gore. Anchor: #SBVXFJBU
- Updated Table 3-21. Table was reformatted. Anchor: #TVDCPEMD
- Under Grades and Profiles, guidance was added for ramp grades stating "For special circumstances and topography conditions, the following grades may be used: Ramp Design Speed 25-30 mph-7% max, 35-40 mph-6% max, and 45 mph or greater-5% max."
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- Corrected title of Section 8 to read Texas Highway Freight Network (THFN).
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- Under Geometric Design, added language for Bridge Width for clarification. Anchor: #DESPCVMT
- Updated Table 4-1. Added footnote "e", changed Horizontal Clearance to Clear Zone, and changed title of table. Anchor: #PEDMNQBS
- Updated Table 4-2. Changed title of table, changed Horizontal Clearance to Clear Zone, and added footnote f. Anchor: #OARQHIPD
- Table 4-2, changed 16' clear zone to 10' clear zone for consistency with 4R clear zone table. Anchor: #NGYRKWFX
- Updated Table 4-3. Changed title of table and changed Horizontal Clearance to Clear Zone. Anchor: #EQFFFPBR
- Under Alignment, added guidance on what is considered a 3R project and a 4R project. Anchor: #ETHTSCFT
- Under Alignment, added guidance on Design Exceptions for 3R projects.
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- Under Safety Design, replaced "accident" with "crash". Anchor: #NNHPUIWD
- Under Safety Design added guidance and bullet item for Crash Analysis. Anchor: #MEVQWRRV
- Under Safety Design, added language for wildlife crashes to section. Anchor: #FOXXYGUP
- Under Safety Design, added guidance for High Friction Surface Treatment (HFST) to address deficiencies in curve radius or superelevation. Anchor: #WDYUWQRJ
- Under Safety Design, added reference to consult with Design Division's Traffic Simulation and Safety Analysis Section for guidance. Anchor: #JVAEENUU
- Under Basic Safety Improvements, added reference to the Traffic Safety Division's Traffic Engineering Standard Sheets.
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- Updated Table 4-4. Corrected Bridge Width to be retained from 22' to 24'. Anchor: #KLQWIYOY
- Updated Table 4-4. Corrected superscript on table.
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- Under Working Agreements, added guidance stating that "TxDOT design standards are used on Park Roads (PR) that lead or enter a state park and are designated on the State Highway System. Parks and Wildlife Roads (PW) will use the standards of Texas Parks and Wildlife Department standards."
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- Under Guidance for Bicycle Facilities, changed "bicycle paths" to "shared use paths". Anchor: #YWPKRVJA
- Under Guidance for Bicycle Facilities, added guidance for what is a bicycle lane, shared lane, and shared use path. Anchor: #HLKOHSED
- Under Guidance for Bicycle Facilities, guidance was added for the preferred order for design is to have a shared use path, then a bike lane, then a shared lane. Anchor: #WPBOPLJG
- Under Guidance for Bicycle Facilities, added guidance that shared lanes are not appropriate on high speed facilities and should be avoided. Anchor: #VLIOWTNJ
- Under Guidance for Bicycle Facilities, added guidance for a striped bicycle lane the clear width is 4' minimum and 5' desirable. Anchor: #HJJOWBQB
- Under Design Exceptions and Design Waivers for Bicycle Facilities added new guidance for design exceptions and design waivers for bicycle lanes, shared lanes and shared use paths.
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- Renamed Section 1 to Longitudinal Barriers and Roadside Safety Hardware Criteria. Anchor: #RKNFYUIF
- Under Guardrail, added guidance stating that "Guardrail should be offset at least 4.0' and desirably 5' or more from the nearest edge of fixed objects." Anchor: #WYCJEPVG
- Under Crash Cushion Categories, added additional guidance on crash cushions. Anchor: #HOKHUUIM
- Under Roadside Safety Hardware Criteria, added language on MASH criteria and guidance.
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- Under Undercrossings, added guidance to provide ample drainage.
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- Removed "Shoulder Texturing" from title and replaced it with "Rumble Strips" in Section 5, and updated guidance on rumble strips to make consistent with Traffic Safety Division RS standards, and FHWA guidance.
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- Updated Table 7-2 and changed Radii for 3-Centered Compound Curve, Symmetric for a 75 degree angle/Passenger vehicle (P) to 100-25-100.
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- Updated Table 8-1. Table was reformatted. Anchor: #QGXVQXRS
- Updated Table 8-2. Table was reformatted. Anchor: #OEHHMFXV
- Updated Table 8-3. Table was reformatted. Anchor: #KIIKLHIJ
- Updated Table 8-5. Table was reformatted. Anchor: #RCITRSFM
- Updated Table 8-6. Table was reformatted. Anchor: #MFUDOAWB
- Updated Table 8-7. Table was reformatted. Anchor: #XSNCBLYR
- Under Superelevation, added guidance for superelevation on bridge structures to begin/end superelevation transition at bridge bent line. Anchor: #TMSDUODW
- Updated Table 8-8. Table was reformatted. Anchor: #WFPDFRQT
- Updated Table 8-9. Table was reformatted.
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- Changed "Horizontal Clearance to Clear Zone". Anchor: #OUTRXSSU
- Updated Table 8-10. Changed title of table and reformatted table. Anchor: #JJHEEQXJ
- Updated Table 8-11. Table was reformatted.
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- Updated Table 8-12. Table was reformatted. Anchor: #IQSTLSMA
- Updated Table 8-13. Table was reformatted.
Appendix A – Longitudinal Barriers
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- Added verbiage giving an overview of Types of Barrier. Added verbiage with illustration defining Working width.
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- Under Rail Element and Blockouts paragraph, added verbiage clarifying rail height and blockout applications.
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- Updated deflection considerations for guard fence; updated Fig.A-6 accordingly.
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- Updated Length of Need Fig-A-8 for additional clarity; added verbiage for the required protection of bridge class culverts. Anchor: #FAUANWUI
- Updated Table A-2.
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- Under Application, for Width of the median, added "(measured from edge of pavement to edge of pavement)." Anchor: #IYUCHISL
- Added additional Cable Median Barrier guidance with respect to placement and appropriate applications. New Fig.A-16.
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- Updated Fig. A-17 & A-18 to provide additional overlap for MBGF and cable barrier applications.
Appendix B – Treatment of Pavement Drop-offs in Work Zones
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- Minor errata updates.
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- Table for Treatment Guidelines for Pavement Drop-offs in Construction Work Zones, update Note 3.
Appendix C – Driveway Design Guidelines
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- Added guidance for support documentation in the form of traffic operations and safety analysis.
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- Clarified definition of driveway and commercial driveway.
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- Clarified pedestrian application guidance at a driveway. Updated Table C-2 and Table C-3 to clarify guidance on divider width in cases of a pedestrian refuge. Anchor: #YFDLJVEF
- Updated Table C-1. Changed title of table and added 15' Min. to table. Anchor: #GSPNUBEE
- Updated Table C-2. Changed footnotes 1 & 2 and added "Min." to table under Radius. Anchor: #BMOAITRF
- Updated Table C-3 footnote 2. Anchor: #QTETQKVM
- Under Divided Driveways, added "…and 6 feet for a Ped. Refuge." For a minimum width of a slightly raised divider.
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- Under General Guidelines, changed the minimum refuge area to 5 x 6 feet.
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- Updated references.
Appendix D – Right-Turn Slip Lane Design Guidelines
New Appendix providing guidance on the design of right-turn slip lanes.
Appendix E – Alternative Intersections and Interchanges
New Appendix providing guidance on the alternative intersection and interchange forms.
This manual, and all revisions, applies to all highway and street project development, whether developed by the department or with consultant staff. Due to projects that may be further along in development with current criteria, this manual, and all revisions, will be effective for all projects beginning with the January 2021 letting. Project development using this manual and its revisions prior to that date is at the option of the district.Anchor: #DLWIXOQL
Contact the Roadway Design Section Director of the Design Division at (512) 416-2678 with any questions or comments.Anchor: #XQEDQKPR
Past manual notices are available in a pdf archive.