State Highway Access Manual

Chapter 4 – Standard Site Access Improvements

This chapter identifies the site access improvements required to support proposed entrances and street connections. The function, applications, and geometric design of various site access improvements, including frontage improvements and turning lanes, are discussed in this chapter. The site access improvements required for different types of development projects, highway functions, and traffic conditions are specified. Some projects may be eligible for exceptions as discussed in 4.11 Exceptions and Special Cases.

4.1   General Requirements

  • 4.1.1 Design Criteria – The design of state highway improvements for site access shall conform to SHA's Standards and Specifications, the guidelines presented herewith, and engineering practices accepted by SHA. Specific engineering design requirements for improvements within the state's right-of-way are discussed in Chapter 5 Technical Design Guide.
  • 4.1.2 Scope of Improvements – The scope of improvements required by SHA to support the proposed access generally reflects the type and size of the development, the number and location of proposed access points, the anticipated traffic conditions, and the functional requirements, operational characteristics, and geometric conditions of the state highway. The State Highway System designation, highway functional classification, prevailing approach speeds, traffic volumes, driver expectancy, sight distance, adjacent access points, nearby intersections, existing lane markings, and other existing and anticipated geometric conditions on the highway are considered during the review process.

  • 4.1.3 Frontage Channelization – Frontage channelization and related highway improvements may be required for any project, in accordance with 4.3 Deceleration Lanes. The construction of barrier curb and gutter along the frontage of developing properties is necessary to delineate the means of vehicular ingress and egress to roadside development. This confines vehicular movements to the permitted entrances, provides an appropriate roadside condition for lower speed highways in urbanized areas, and affords protection for pedestrians on adjacent sidewalk. Along higher speed highways, roadside grading using relatively flat slopes provides an appropriate treatment for the safety of errant vehicles. Curb and gutter may be reduced or eliminated in many rural applications where appropriate roadside grading is feasible.

    In any development setting, the necessary highway improvements may include roadside grading, storm drainage, traffic control measures, utility relocation, and adjustment of various highway features. SHA may require the design of frontage improvements to be coordinated with long-term highway plans, local master plans, or other construction projects, thereby reducing or minimizing future impacts, costs, and traffic disruption.

  • 4.1.4 Turning Lanes – Turning lanes typically include deceleration lanes, acceleration lanes, bypass lanes, and left-turn lanes. They may be required in accordance with 4.4 Acceleration Lanes to address right and left turns both in and out of an access point. Turning lanes are an important element of site access improvements in that they allow speed changes and turning maneuvers to occur outside of the normal flow of highway traffic. This reduces the incidence of rear-end collisions at the access point and helps to maintain through-traffic flow on the highway. Accordingly, SHA requires turning lanes for public road connections and for commercial sites that will generate appreciable traffic during times of peak travel on the state highway.

  • 4.1.5 Improved Shoulders – Where formal turning lanes are not expressly required by this policy, widening to provide an improved shoulder may be required for any access point to address occasional turning vehicles, in accordance with 4.7 Other Auxiliary Lanes. This includes providing new shoulders, widening along existing shoulders, and reconstructing existing shoulders to provide a traffic bearing surface outside of the normal travel lanes of the highway to address occasional turning movements.

  • 4.1.6 Limits of Improvements – The existing highway shall be widened as necessary to support the required frontage channelization, turning lanes, and improved shoulders and provide appropriately-designed transitions between improved and unimproved segments of the highway. Applicants are advised that the required widening may extend beyond the developing property frontage. For this reason, the availability of sufficient right-of-way to construct acceptable turning lanes must be considered when determining the location of proposed access. If sufficient right-of-way is not available, SHA may require the applicant to use a different access point location where the normally-required features are feasible.

  • 4.1.7 Prior Improvements – Improvements proposed for a new project shall not adversely affect, diminish, or otherwise compromise the effect of improvements previously constructed for another project, unless specifically authorized by SHA. For example, previously-built acceleration and deceleration lanes that serve an existing development may not be eliminated to accommodate a left turn lane into a new development on the opposite side of the highway.

4.2   Frontage Channelization

  • 4.2.1 Curb and Gutter Limits – Curb and gutter channelization of developing property frontage is required in accordance with Table 4.2.1. Consideration is given to the progression of adjacent land development and build-out of the highway, along with the anticipated ultimate highway typical section, in determining whether full frontage channelization should be required.
  • 4.2.2 Exceptions – Channelization may be waived in the following instances, unless a safety issue results:

    • 4.2.2.A. The site frontage is located in a historically or environmentally sensitive area, as demonstrated by the applicant and accepted by the SHA.
    • 4.2.2.B. The topography along the property frontage is flat, the grade of the highway along the frontage is less than 0.5%, and an open section would be preferable from a drainage standpoint.
    • Table 4.2.1 Standard Frontage Channelization

      Application Channelization Required
      All
      Along any proposed sidewalk, where the use of barrier curb is acceptable.*
      Where roadside grading conforming to 5.6.4 Width of Left Turn Lanes and Center Turn Lanes is not feasible but the use of barrier curb is acceptable.
      Fully Developed Urban Areas
      Commercial Entrance proper
      Property corner to property corner
      Residential Street connection proper
      Property corner to property corner
      Developing Areas
      Commercial Entrance proper
      Property corner to property corner
      Commercial – with large frontage (1,500' or more) along a state highway Entrance proper
      Within the limits of the developed area/lot(s), except where neighboring property has existing curb and gutter and/or neighboring property is zoned commercial, in which case a full frontage improvement may be required for highway continuity.
      Residential Street connection proper
      Property corner to property corner, where a closed-section highway exists, or is anticipated, along adjoining property frontage for highway continuity.
      Along a 10' minimum tangent on each side of the street connection, where the highway is expected to remain an open section and a roadside design conforming to 5.6.4 Width of Left Turn Lanes and Center Turn Lanes is proposed.
      Where posted speed is 40 mph or less and an open-section highway exists and is anticipated to remain open, curb and gutter is required only along the designated full-width travel way of acceleration lanes, deceleration lanes, and shoulder improvements.
      Rural Areas
      Commercial/ Industrial, any frontage Entrance proper
      Along the developed portion of the site, except where neighboring property has existing curb and gutter along the frontage, in which case a full frontage improvement may be required for highway continuity.
      Channelization may be limited to the entrance proper (radius returns) plus 10' tangents on each side of the entrance along open section highways where there is an appropriate physical barrierto prevent unauthorized access.
      Residential None required
      *NOTE: Requirement may be waived for sidewalks and/or recreational trails located outside of the roadside recovery area as established in 5.7.4 Roadside Grading

4.3   Deceleration Lanes

  • 4.3.1 Function – Substantial speed reduction is normally required by vehicles making right turns into site and subdivision access points. Due to site constraints and practical limitations on their geometric design, the safe operating speed for commercial entrances and street connections is typically in the 5 to 15 mph range. Moreover, limited separation between the highway and on-site traffic patterns may result in vehicle stacking at or near the entrance area. Where vehicles must reduce speed considerably and/or stop in the through lane in order to make right turns into access points, the potential for rear-end collisions is increased.

    Deceleration lanes reduce the risk of rear-end collisions by allowing speed reduction and right turns to take place outside of the highway through-lanes. Depending on their length, either full or partial speed adjustment can occur within the deceleration lane, thereby reducing speed differentials and associated traffic disruption in the through-lanes. The importance of providing for complete speed adjustment is increased with greater right-turning and/or approach volumes and higher operating speed. In addition, the function of the highway must be considered. For example, full-speed change lanes may be appropriately required for any access along controlled-access highways and highly-traveled arterial routes in order to minimize adverse effects on their capacity and service conditions. In contrast, an improved shoulder may be acceptable, in lieu of a formal deceleration lane, for relatively minor development along low-speed routes that provide a collector function.

  • 4.3.2 Warrants – Deceleration lanes may be required for any access point deemed necessary by SHA to provide acceptable safety and traffic operations on the state highway. In the absence of compelling site-specific considerations, deceleration lanes are required in accordance with the criteria given in Table 4.3.2:
  • Table 4.3.2 Deceleration Lane Warrants

    Application Standard Requirement
    Primary Highways – Fully-Controlled Access
    Approved Interchange Exit Ramp Full deceleration lane is required
    Primary Highways – Partially-Controlled Access
    Approved Intersection
    Right Turn from Highway
    Full deceleration lane is required
    Primary Highways – Uncontrolled Access
    Approved Commercial Entrance
    or Street Connection
    Full deceleration lane may be required
    Otherwise, refer to the requirements for Secondary Highways
    Secondary Highways
    Commercial Entrance
    Right Turn from Highway
    Full deceleration lane is required if a dedicated right-turn lane is necessary for acceptable traffic operations at the access point(s), based upon accepted traffic analysis.
    Full deceleration lane is required if 30 or more peak-hour right turns are expected at the access point(s).
    Partial deceleration lane is required if 10 to 29 peak-hour right turns are expected at the access point(s).
    Otherwise, a shoulder improvement may be required in lieu of a deceleration lane. Refer to 4.6 Shoulder Improvement.
    Street Connection
    Right Turn from Highway
    Full deceleration lane is required if the total # lots served is more than 12
    Partial deceleration lane is required if the total # of lots served is 6 to 12
    Shoulder improvement is required if the # of lots is less than 6. Refer to 4.6 Shoulder Improvement.
  • 4.3.3 Length Required – The length of Standard Full Deceleration Lanes and Standard Partial Deceleration Lanes will be as discussed below.

    • 4.3.3.A. Standard Full Deceleration Lanes – The length of Standard Deceleration Lanes is based on AASHTO design for speed change and transition tapers, plus any applicable queuing for right turns into the access point. Right-turn queuing length under the design operating conditions, based on the results of an approved traffic study, is to be added to the required lane length given below. Neglecting queuing, the minimum lengths are as follows for various posted speeds:
    • Table 4.3.3.A Length Required for Full Deceleration Lanes

      Posted Speed (mph) 30 40 50 55
      Total Length 425' 535' 630' 670'
      Min. Approach Lane Length 325' 435' 530' 570'
      Min. Approach Taper Length 100' 100' 100' 100'
      *NOTE: Full width pavement is required along the total length of the improvement. The taper is to be established via pavement markings.
      *NOTE: Approach lane length is approximately equal to the AASHTO deceleration length based on deceleration to a stop condition from a design speed of 10 mph above the posted speed.
      *NOTE: Approach taper length shall be consistent with AASHTO policy. The 100’ minimum length stated is for urban areas. A 15:1 taper rate is appropriate in rural areas for highways with operating speeds above 30 mph.
    • 4.3.3.B. Standard Partial Deceleration Lanes – The layout of Standard Partial Deceleration Lanes is as follows:

    • Table 4.3.3.B Length Required for Partial Deceleration Lanes

      Posted Speed (mph) 30 40 50 55
      Total Length 150' 250' 350' 400'
      Min. Approach Lane Length 50' 150' 250' 300'
      Min. Approach Taper Length 100' 100' 100' 100'
      *NOTE: Full width pavement is required along the total length of the improvement. The taper is to be established via pavement markings.
      *NOTE: Total length is approximately equal to the AASHTO deceleration length based on deceleration to a stop condition from a design speed of 10 mph below the posted speed.
      *NOTE: Approach taper length shall be consistent with AASHTO policy. The 100’ minimum length stated is for urban areas. A 15:1 taper rate is appropriate in rural areas for highways with design speeds above 30 mph. In rural areas, this may require allocating more of the specified total length to the approach taper.

4.4   Acceleration Lanes

  • 4.4.1 Function – Acceleration lanes allow vehicles turning out of an access point to gain speed before merging into the highway through-traffic. Depending on their length, acceleration lanes afford either full or partial speed adjustment outside of the normal travel lanes, contributing to safer operating conditions. Full speed adjustment is most important where a relatively high volume of turning vehicles is expected to freely merge with through-traffic at the highway operating speed. In this case, the acceleration lane is vital to the safe and effective operation of the intersection or interchange. Full-speed change lanes are also appropriate for controlled-access highways and other high-speed, high-volume arterial routes. Partial speed adjustment is sufficient for the vast majority of stop-controlled access points. This practice addresses outbound movements that occur during gaps in through-traffic by providing a tapered area for some speed adjustment and merging.
  • 4.4.2 Warrants – Acceleration lanes may be required for any access point deemed necessary by SHA to provide acceptable safety and traffic operations on the state highway. In the absence of compelling site-specific considerations, acceleration lanes are required in accordance with the criteria given in Table 4.4.2.

  • Table 4.4.2 Acceleration Lane Warrants

    Application Standard Requirement
    Primary Highways – Fully-Controlled Access
    Approved Interchange Entrance Ramp Full acceleration lane is required
    Primary Highways – Partially-Controlled Access
    Approved Intersection
    Right or Left Turn onto Highway
    Full acceleration lane is required
    Primary Highways – Uncontrolled Access
    Approved Commercial Entrance
    or Street Connection
    Full acceleration lane may be required.
    Otherwise, refer to the requirements for Secondary Highways.
    Secondary Highways
    Commercial Entrance or Street Connection Free Flow Right or Left Turn onto Highway Full acceleration lane is required if a speed change lane is necessary to facilitate safe and free-flow merging at design traffic volumes and operating speeds, as determined by SHA.
    Otherwise, a partial acceleration lane is required
    Commercial Entrance Stop-Controlled Right Turn onto Highway Full acceleration lane is required if necessary for safe and acceptable traffic operations, as determined by SHA.
    Partial acceleration lane is required if 30 or more peak-hour right turns are expected.
    Otherwise, a shoulder improvement is required in lieu of an acceleration lane. Refer to 13.6 Shoulder Improvement.
    Commercial Entrance Stop-Controlled Left Turn onto Highway Full acceleration lane or partial acceleration lane is required if necessary for safe and acceptable traffic operations, as determined by SHA.
    Otherwise, turns are received by the through lane.
    Street Connection Stop-Controlled Right Turn onto Highway Partial acceleration lane is required if the total # of lots served is more than 12
    Shoulder improvement is required in lieu of an acceleration lane if the total # of lots served is 6 to 12. Refer to 13.6 Shoulder Improvement.
    Shoulder improvement may be required in accordance with 13.6 Shoulder Improvement if the total # of lots served is 2 to 5.
  • 4.4.3 Length Required

    • 4.4.3.A. Full Acceleration Lanes - The length of full acceleration lanes will be determined based on the requirements for speed change and applicable weaving/gap acceptance, in accordance with the latest AASHTO guidelines.
      • (1) The required acceleration length shall be determined assuming acceleration from a stop condition at the access point to the design speed of the highway.
      • (2) The design speed of the highway shall be assumed to be 10 mph above the posted speed, unless otherwise indicated by an approved speed study.
      • (3) When supported by appropriate geometric design and traffic analysis, it may be reasonable to assume other than a stop condition at the access point. In this case, SHA may accept a reduced acceleration length.
      • (4) An appropriate taper shall be provided at the end of any full acceleration lane. The taper length is in addition to the required acceleration length. For controlled-access highways, a 300' taper is consistent with current AASHTO policy.
    • 4.4.3.B. Partial Acceleration Lanes – The length of standard partial acceleration lanes will be as follows:
    • Table 4.4.3.B Length Required for Partial Acceleration Lanes

      Posted Speed (mph) 30 40 50 55
      Total Length * 250' 360' 560'
      Min. Departure Lane Length * 100' 180' 380'
      Min. Departure Taper Length * 150' 180' 180'
      *NOTE: Full width pavement is required along the total length of the improvement. The taper is to be established via pavement markings.
      *NOTE: (*) For posted speeds less than 40 mph, a 150' departure taper may be required. This would be in addition to the minimum 10' tangent section of curb and gutter, as discussed elsewhere.
      *NOTE: Total length is approximately equal to the AASHTO acceleration length for acceleration from an assumed stop condition to a design speed of 10 mph below the posted speed.

4.5   Left Turn and Bypass Lanes

  • 4.5.1 Function – Left turn movements encounter delays while waiting for gaps in opposing traffic, in addition to other vehicles at the intersection or access point. As the volume of opposing traffic increases, left turn delays become a strong possibility at any intersection. Vehicles stopped in the through-lanes while waiting to make left turns present multiple safety hazards, causing other vehicles to rapidly stop or change lanes in order to avoid them. Left-turning vehicles stopped in a through-lane can drastically reduce the safety and service conditions of the highway by increasing the possibility of rear-end collisions and impeding through-traffic flow. Accordingly, the volumes of left-turning and opposing vehicles are critical factors in the evaluation of intersection capacity, delays, queuing, and traffic signal timing.

    As the volume of opposing traffic and/or left-turning vehicles increases, queuing of vehicles waiting to execute left turns is more likely to occur. Left-turn lanes substantially improve the safety and operation of intersections and median crossovers on multilane highways. Their design combines the function and benefits of deceleration lanes with storage capacity for queuing of vehicles waiting to make left turns. Left-turn lanes allow speed reduction and queue storage to take place outside of the normal travel lanes, thereby reducing the likelihood of rear-end collisions and reducing the disruption of through-traffic.

    Bypass lanes are often employed on two-lane undivided highways to accommodate occasional left-turning vehicles at “T” intersections without affecting the location of existing through-lanes. The bypass lane allows through-traffic to maintain travel at the posted speed while passing to the right of a vehicle stopped in the normal travel lane waiting to execute a left turn. Where frequent queuing of left turning vehicles may be expected on two-lane highways, a dedicated left-turn lane may be necessary instead of a bypass lane. Larger commercial sites and subdivisions, particularly those on higher volume routes, will typically require a dedicated left-turn lane as opposed to a bypass lane. In general, left-turn lanes are appropriately provided when a 4th leg is introduced to an existing “T” intersection.

  • 4.5.2 Warrants – Bypass lanes or left-turn lanes may be required for any access point deemed necessary by SHA to provide acceptable safety and traffic operations on the state highway. The volume of left-turning vehicles and the volume of traffic in the opposing travel lane are important but not exclusive factors considered by SHA. The charts in Left Turn Lanes and Bypass Lane Guidance may be used as a general indicator of traffic volumes that may warrant a bypass lane or left-turn lane.

    In the absence of compelling site-specific considerations, bypass lanes or left-turn lanes are required in accordance with the criteria given in Table 4.5.2:

  • Table 4.5.2 Left Turn/Bypass Lane Warrants

  • Application Standard Requirement
    Primary Highways – Partially Controlled or Uncontrolled Access
    Multilane Divided Left-turn lane is required for any approved intersection.
    Multilane Undivided Left-turn lane is required for any approved intersection.
    Two-Lane Undivided Left-turn lane or bypass lane is required; the selection will be made by SHA.
    Secondary Highways
    Multilane Divided Left-turn lane is required for any intersection or median crossover.
    Multilane Undivided Left-turn lane may be required if warranted based on results of an approved traffic study or due to safety considerations.
    Two-Lane Undivided Left-turn lane may be required for commercial sites and subdivisions of any size based on the results of an approved Traffic Impact Study. The guidelines in Left Turn Lanes and Bypass Lane Guidance shall be used to facilitate a determination.
    Left-turn lane may be required where a left-turn lane is preferred over a bypass lane due to safety or practical considerations
    Where an additional access point is proposed opposite an existing “T” intersection, left-turn lanes shall be required instead of a bypass lane.
    Bypass lane is required for street connections that will serve a total of more than 12 residential lots, if a left-turn lane is not warranted.
    Bypass lane may be required for street connections that will serve a total of 6 to 12 residential lots, based on review of site-specific safety and traffic conditions. Otherwise, an improved shoulder may be required. Refer to 13.6 Shoulder Improvement.
    An improved shoulder may be required for street connections that will serve a total of 2 to 5 residential lots. Refer to 13.6 Shoulder Improvement.
  • 4.5.3 Geometric Layout for Left Turn Lanes

    • 4.5.3.A. General – When a left-turn lane is required by SHA as part of the approved access-related improvements for a development, the design of the lanes must adhere to the latest version of AASHTO's A Policy on Geometric Design of Highways and Streets and FHWA’s Manual on Uniform Traffic Control Devices.
    • 4.5.3.B. Length of Turn Bay – The design shall incorporate the appropriate approach taper length, deceleration length, and queue storage length:

      Total Length = Taper Length + Deceleration Length + Storage Length

      The required deceleration length varies according to the posted speed and functional classification of the highway. This yields the following standards to be applied:

    • Table 4.5.3 Left Turn Bay Lengths
    • (QUEUE STORAGE NOT INCLUDED – MUST BE ADDED)
    • Full Deceleration Design

      Applies to:
      Primary Highways – Any
      Secondary Highways – Arterial, Divided
      Secondary Highways – Any, where warranted for safety/traffic operations
      Posted Speed (mph) 30 40 50 55
      Total Length 425' 535' 630' 670'
      Min. Lane Length 325' 435' 530' 570'
      Min. Taper Length 100' 100' 100' 100'
      Partial Deceleration Design

      Applies to:
      Secondary Highways – Arterial, Undivided
      Secondary Highways – Collector, Divided or Undivided
      Secondary Highways – Any, where warranted for safety/traffic operations
      Posted Speed (mph) 30 40 50 55
      Total Length 150' 250' 350' 400'
      Min. Lane Length 50' 150' 250' 300'
      Min. Taper Length 100' 100' 100' 100'
      *NOTE: Full width pavement is required along the total length of the improvement. The taper is to be established via pavement markings.
      *NOTE: Refer to 4.3 Deceleration Lanes for discussion and derivation of full and partial deceleration lengths incorporated into the requirements above.
    • 4.5.3.C. Storage Length – The required storage length shall always be consistent with the results of an approved traffic study. Storage length shall be determined from an appropriately-supported queuing analysis. For passenger vehicles with arrival times distributed throughout the peak hour, the following formula may be used as a guide:

      Queue Storage Length Required = 1.25 X (# of peak hour left turns)

      Where a storage length less than 50’ is indicated, the left-turn lane lengths given in Table 4.5.3 Left Turn Bay Lengths above will be considered sufficient to address queue storage.

      Additional storage length may be required to address school bus, truck, or other commercial vehicle traffic characteristics, as determined by SHA.

    • 4.5.3.D. Lane Shift – When a left turn lane is established on an existing two-lane undivided highway, appropriate lane shift tapers for the through-lane movements shall be provided in accordance with the latest version of the MUTCD:

      Design Speed Taper Length Formula
      40 mph or less Taper Length (ft) = Lateral Shift (ft) X [Design Speed (mph)]2
      60
      Over 40 mph Taper Length (ft) = Lateral Shift (ft) X Design Speed (mph)

      The lane shift taper is a separate requirement, not to be confused with the left-turn bay taper discussed in 4.5.3.B.

    • 4.5.3.E. Closely-Spaced Intersections – Where closely-spaced intersections and/or access points would result in overlapping left-turn bays and/or lane shift transitions, SHA may require the construction of an extended center-turn lane or reduce the required length of the left-turn lane. If the minimum queue storage required by 4.5.3.C cannot be achieved by the design, SHA may deny access for the left-turn movement.
  • 4.5.4 Bypass Lanes The layout of bypass lanes shall conform to the standards given in this section.
    • 4.5.4.A. Length – The length required for bypass lanes varies with the operating speed of the highway and shall be in accordance with Table 4.5.4. Tapers are longer for higher-speed highways to allow for safe lane shifts and clearance from left-turning vehicles.
    • Table 4.5.4 Standard Lengths for Bypass Lanes

    • Posted Speed (mph) Approach Taper Approach Lane Departure Lane Departure Taper Total Bypass Lane Length
      30 150' 200' 200' 150' 700'
      40 200' 200' 200' 200' 800'
      50 300' 200' 200' 300' 1000'
      55-60 360' 200' 200' 360' 1120'
      *NOTE: Taper lengths are based on the MUTCD taper design for lane shift in temporary traffic control zones, which is one-half the length normally required for a permanent through-lane shift.
    • 4.5.4.B. Urban Areas – In urban areas, the approach taper may be reduced to 100' with the difference applied to increase the approach lane length.

    • 4.5.4.C. Adjacent Intersections – Additional length may be required to form a functional auxiliary lane to address closely-spaced street connections and/or commercial entrances along the highway.
    • 4.5.4.D. Reduced Lane Lengths – The length of the approach lane and departure lane portions of the bypass lane may be reduced to 150' and 100', respectively, for the following applications:
      • (1) Residential subdivision access serving 12 lots or less.
      • (2) Commercial sites that only marginally warrant a bypass lane, when acceptable to the Assistant District Engineer - Traffic.
    • 4.5.4.E. Use of Existing Turning Lanes – Where there are existing acceleration and/or deceleration lanes serving an access point on the opposite side of the highway, the applicant may be required to upgrade those facilities to function additionally as a bypass lane for the new access. However, the existing turning lanes may not be eliminated or otherwise compromised to support improvements for the new access. Consideration shall be given to establishing opposing left-turn lanes instead.
    • 4.5.4.F. Left-Turn Lane Alternative – A left-turn lane may be approved in lieu of a bypass lane, at SHA's discretion, where a bypass lane would not be feasible or cost-effective. Factors considered include lane shift, highway function, and site-specific traffic and safety conditions. In some cases, a shoulder improvement may be preferable to a left-turn lane when a bypass lane is not feasible.

4.6   Shoulder Improvement

Shoulder improvement is defined as the construction of new shoulders, or widening and reconstruction and/or resurfacing of existing shoulders, to provide a traffic-bearing paved area outside of the normal travel lanes for accommodating turning movements at the proposed site access.

  • 4.6.1 Warrants – A shoulder improvement may be required where indicated by one or more of the following guidelines:
    • (1) Along and throughout the limits of any frontage channelization required by 4.2 Frontage Channelization.
    • (2) Where a full or partial deceleration or acceleration lane is not required.
    • (3) Where a bypass lane is not required.
    • (4) Where a deceleration, acceleration, and/or bypass lane is required but is not feasible, as determined by SHA, due to substantiated site constraints (lack of sufficient available right-of-way, lack of alternate access location with sufficient right-of-way, prohibitive environmental impacts, etc. – but not economic hardship).
    • (5) Where warranted for safety, as determined by SHA.
  • 4.6.2 Length Required – The length required for a shoulder improvement varies with the intended use, as follows:

  • Application/Movement Length Required
    Posted Speed < 40 mph Posted Speed 40 mph or over
    Frontage Improvement Refer to 4.2 Frontage Channelization Refer to 4.2 Frontage Channelization
    Deceleration/Right-Turn Based on 8:1 taper* Based on 15:1 taper*
    Acceleration Based on 8:1 taper* Based on 15:1 taper*
    Bypass Refer to 4.5 Left Turn and Bypass Lanes Refer to 4.5 Left Turn and Bypass Lanes
    Other Case-by-case Case-by-case
    *NOTE: Assuming 12' of the available shoulder width is used by turning vehicles, the lengths are approximately 100' and 180' for 8:1 and 15:1 tapers, respectively.

4.7   Other Auxiliary Lanes

Requirements with respect to the construction or modification of other auxiliary use lanes, such as two-way center-turn lanes, continuous auxiliary lanes, and service roads, will be determined by SHA on a case-by-case basis. The design shall be based on AASHTO geometric design guidelines and accepted engineering practices, addressing the anticipated traffic safety and operational conditions.

  • 4.7.1 Continuous Auxiliary Lane – Where there is limited distance available between successive turning lanes along the highway, extension of the proposed improvements may be required to provide a continuous auxiliary lane. This requirement is most common in urban settings where access points and median crossovers may be closely spaced and along high-speed highways with acceleration, deceleration, and left-turn lanes having considerable length.
  • 4.7.2 Center Turn Lane – SHA may require the permittee to provide a center-turn lane for handling left-turn traffic where warranted to address traffic impacts from development. Typical applications include urban highways with closely-spaced, full-movement access points for which individual left-turn bays are not feasible and for which minimal queueing of left-turning vehicles is anticipated. While center-turn lanes are sometimes established on 2-lane and multilane undivided highways, often through retrofit of new pavement markings, their use will not be considered on divided highways or highways pending construction of a raised median.

  • 4.7.3 Service Road – Appropriately designed permanent or temporary service road segments may be required in connection with proposed access where necessary to address future highway needs.

4.8   Back Curb

  • 4.8.1 Warrants – Back curb may be required along the existing or proposed right-of-way line to control access to the state highway right-of-way from the development. The on-site curb and gutter typically required for commercial development is normally sufficient for this purpose, in lieu of a back curb. In rural areas where a drainage ditch of sufficient depth to act as a barrier will remain paralleling the highway, or the height and grade of slope of the property abutting the state highway is greater than 3’ and 2:l respectively, the back curb (on the right-of-way line) may be eliminated at the discretion of SHA. If the topography of the area is changed by the owner so that the side ditches or cut slopes are eliminated, a curb or a curb and gutter along the right-of-way will be required.
  • 4.8.2 Layout – On-site curb shall be constructed along parking areas, drive aisles, and other areas subject to motor vehicle traffic. It shall be located beyond the ultimate reserved or dedicated right-of-way required for future public road improvements with allowance made for local zoning or setback requirements. SHA identifies the ultimate section based on SHA planning studies, design plans, or the Highway Needs Inventory, as applicable. When back curb is required instead of on-site curb, the following guidelines apply:

    • (1) Where existing right-of-way is sufficient for the ultimate highway improvements, the rear edge of the back curb shall be constructed on the existing right-of-way line.
    • (2) Where the existing right-of-way is not sufficient to contain the ultimate improvements, the curb should be placed on the alignment of the proposed right-of-way line just outside the limits of dedication or reservation, as applicable.

4.9   Highway Medians

Construction of new or modified highway medians may be required in order to restrict, discourage, or prevent certain turning movements in and/or out of the site. This requirement is determined by evaluating the safety and traffic operations issues presented at each point of access. Median installation and modifications most commonly include:

  • (1) Construction of a raised median in place of an existing two-way (continuous) left-turn lane to prevent left turns in and out of the site.
  • (2) Construction of a raised median to provide protected left-turn lanes separated from through-traffic.
  • (3) Construction of a traffic control island within an existing median crossover to define and/or prohibit certain movements.
  • (4) Construction of a raised median in place of an existing graded, grass median to address safety concerns presented by reduced median width due to widening into the median.
  • (5) Modifying an existing median to allow or deny left-turn access in and/or out of the site.
  • (6) Modifying an existing median opening to allow for double left turns.
  • (7) Extending existing median or turn-lane channelization in front of the site or at a signal-controlled intersection.
  • Requirements will be determined for the specific location on a case-by-case basis. The design of all medians shall comply with AASHTO geometric design guidelines and SHA standards. Suggested geometric layouts for the most common median openings are provided in the typical details in Standard Road Widening and Paving Details.

4.10 Sidewalk

Sidewalk along a state highway may be required by SHA, the local government, or both in connection with a request for state highway access. In either case, the sidewalk construction and/or reconstruction along the state highway(s) will be required and included in the Access Permit. Once constructed, sidewalks are maintained and repaired by the political subdivision in which they are located, not by SHA. The design must conform to SHA's and the local government's requirements.

  • 4.10.1 Warrants – The construction or reconstruction of sidewalks is required in the following instances:
    • (1) In urban areas where appreciable pedestrian traffic along the highway is known or projected, particularly in close proximity to mass transit and other public facilities.
    • (2) Where significant pedestrian traffic is generated by the development and a sidewalk is deemed necessary by SHA for pedestrian safety.
    • (3) Where a critical link to an existing pedestrian network is needed.
    • (4) Where requested by the local government and/or required through the local development approval process.
  • Sidewalk is generally required only along the frontage of the developing property however in some instances it may be required elsewhere along the highway if increased pedestrian travel demand generated by the development causes a safety issue.
  • 4.10.2 Location – The location of the sidewalk shall be determined using practices approved by the appropriate local jurisdiction and/or SHA. Typically, the sidewalk is to be constructed parallel to and behind curb-and-gutter. A 6’ grass strip between the back of curb and the sidewalk is desirable.

  • 4.10.3 Width – Standard width for sidewalk constructed within the state right-of-way is 5' minimum.

  • 4.10.4 Americans with Disabilities Act (ADA) Compliance – All sidewalk facilities constructed within state right-of-way, regardless of the local jurisdiction's requirements, shall comply with ADA standards and practices. Refer to 4.11 Exceptions and Special Cases for additional information and reference to guidance documents.

4.11   Exceptions and Special Cases

Exceptions to the requirements of this chapter may be considered for the following applications, upon receipt of proper supporting documentation, which may include a traffic study. Upon review of a properly-supported appeal, SHA’s decision will be final. No further appeals will be considered once this decision is rendered.

  • 4.11.1 Low-Volume Highways – If the state highway has less than 2,000 ADT and no significant long-term growth in traffic volumes is expected, the scope of site and subdivision access improvements may be reduced at the sole discretion of SHA upon consideration of the safety and operational impact of the proposed access on a case-by-case basis.
  • 4.11.2 Previously-Improved Highway Frontage – The requirement for construction of dedicated turning lanes to exclusively serve the site access may be waived for development along previously-improved highway frontage at the sole discretion of SHA upon acceptable demonstration of at least one of the following requirements (A, B, or C):

    • 4.11.2.A. Insignificant Traffic Impacts
      • (1) The proposed development will result in either no net gain or a net reduction in trip generation during peak-hour periods.
      • (2) The lane configurations and geometric layout of the existing highway can safely accommodate the proposed ingress and egress movements; and
      • (3) No safety or operational problems pre-existed; and
      • (4) No further widening of the highway for capacity improvement is anticipated
    • 4.11.2.B. Adequate Auxiliary Lanes
      • (1) In addition to at least one through-lane, there is an existing curb lane that functions as an auxiliary lane with adequate capacity to safely accommodate the site-generated turning movements; and
      • (2) No further widening of the highway for capacity improvement is anticipated.
      • The determination of adequate capacity will be made by SHA. The applicant may be required to submit a traffic study in order to facilitate this determination.
    • 4.11.2.C. Prohibitive Impacts
      • (1) The standard widening would result in excessive impacts to adjacent properties, the environment, utilities, and/or prohibitively impact the financial viability of the project; and
      • (2) The lane configurations and geometric layout of the existing highway and feasible improvements can safely accommodate the proposed ingress and egress movements; and
      • (3) No safety or operational problems are known to exist.
  • 4.11.3 Channelization Requirements Not Waived – Where the requirement for site-specific turning lanes is waived, frontage improvements may still be required. These may include replacement of existing curb-and-gutter at a new offset to establish a usable shoulder, comply with current bicycle compatibility standards, ensure proper drainage, address maintenance concerns, or accommodate a planned typical section improvement on the state route. An example of a planned typical section improvement is the conversion of a 4-lane undivided section to a 5-lane section with continuous left-turn lanes or a raised median.

  • 4.11.4 Multi-Lane Highways – In general, widening for new acceleration and deceleration lanes for the proposed site access is not required on existing closed-section highways with 6 or more existing travel lanes (3 in each direction), unless the need is identified in an approved traffic impact study or a highway capacity improvement is identified in the Consolidated Transportation Program. This exception shall not apply where precluded by safety considerations.

  • 4.11.5 Development in Sensitive Areas – Developments in historically, environmentally, or culturally sensitive areas, as determined by SHA, will be evaluated on a case-by-case basis. Widening may be waived or reduced in scope, subject to the same conditions as identified in Section 4.11.2 Previously-Improved Highway Frontage above. Frontage improvements may still be required.

  • 4.11.6 Low-Volume Commercial Traffic Generators – The following guidelines may be applied to small-scale commercial development along low (2,000 ADT) to moderate (5,000 ADT) volume highways, at the discretion of SHA, unless a safety issue results:

    • (1) No improvements will be required for a business operating in a residence, with 5 parking spaces or less, which generates less than 50 vehicle trips per day, except as necessary for safety reasons.
    • (2) Limited improvements will be required for businesses which generate less than 50 vehicle trips per day, with 5 parking spaces or less. Typically, the improvements will be limited to establishing a standard paved, channelized commercial entrance. Widening typically will not be required however a shoulder improvement and/or channelization may be required on a case-by-case basis.
    • (3) Businesses which generate greater than 50 vehicle trips per day, but less than 200, will generally require the standard acceleration and deceleration lanes and frontage improvements however bypass lanes will generally not be required.
    • (4) Businesses which generate greater than 200 vehicle trips per day will generally be subject to the full scope of improvements as described elsewhere in this chapter.
  • 4.11.7 Limited Use or Specific Purpose Access – Access that will have use limited to specific time periods or by specific vehicles will be evaluated on a case-by-case basis to determine the scope of site access improvements required. Examples include mining/land reclamation operations, seasonal business operations, temporary business establishments, timber harvesting operations, school bus entrances, loading dock access, telecommunications tower sites, unmanned utility facilities, etc. SHA may require the full scope of improvements normally required in any case.

  • 4.11.8 Frontage Improvements for Site Redevelopment – The requirement for existing site frontage to be improved is determined on a case-by-case basis for redevelopment projects. To the degree to which substandard features or conditions are present, their significance to the safety and operations of the state highway and the extent to which the redevelopment may exacerbate them are prime considerations for SHA. Where no compelling safety, capacity, or operational issue exists, the overall scope of the project is the main consideration. Complete site reconstruction generally requires the same improvements as new construction would, whereas minor site renovations to support a different use may only trigger entrance improvements.

  • 4.11.9 Special Hardship Situations – From time to time, special situations occur which warrant a restrained approach to the application of access requirements. Relief may be possible for the following situations:

    • 4.11.9.A. Expansion of Existing Business – Improvements to existing access may be waived for a functioning business which expands its facilities, upon acceptable demonstration of all of the following:
      • (1) The increase in site-generated traffic attributable to the expansion will be less than 25% of the traffic volume under existing conditions.
      • (2) No change in use or occupancy is proposed.
      • (3) No new points of access are proposed.
      • (4) No safety or operational issues are presented by the existing access conditions or by the increase in traffic generation.
      • (5) No improvements are necessary to ensure consistency and design compatibility with a programmed highway improvement project.
    • 4.11.9.B. In-Kind Replacement – Improvements to existing access will be waived if a building is destroyed and replaced in-kind with no change in use or occupancy and where no safety or operational problems pre-existed.

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