MDOT SHA Access Manual

Chapter 2 – Entrance Design Standards

This chapter presents the Maryland Department of Transportation State Highway Administration (MDOT SHA) Entrance Standards for commercial and industrial sites. These standards apply to new entrances and the modification of existing entrances.

2.1 Types of Entrances and Their Applications

The following guidelines identify appropriate applications for different types of commercial entrances. Selection of the appropriate type of entrance should be made by considering the function, physical characteristics, and traffic conditions of the state highway.

2.1.1 Depressed Curb Entrances
- 2.1.1.A. Description – Depressed curb entrances offer the most compact entrance layout and accommodate two-way movements. The flared sides are equivalent to approximately a 5’ radius return, limiting the speed of vehicles turning into or out from the entrance. Depressed curb entrances provide no directional control.
- 2.1.1.B. Applications
  - (1) Depressed curb entrances are appropriate for use along lower speed highways in urban settings where significant pedestrian traffic is anticipated and highway capacity issues are not a primary concern. The posted speed should be no higher than 40 mph.
  - (2) In the interest of minimizing traffic interference due to turning vehicles, depressed curb entrances shall not be used on primary highways.
  - (3) Refer to MD 630.01, MD 630.02, and MD 630.03 of the SHA Book of Standards.
2.1.2 Commercial Two-Way Entrances
- 2.1.2.A. Description – Commercial two-way entrances allow for inbound and outbound movement between curbed sides. The entrances provide no directional control, allowing full movement access. A minimum radius accommodates turning movements more easily than a depressed curb entrance of the same throat width.
- 2.1.2.B. Applications
  - (1) Commercial two-way entrances are appropriate for use along an undivided highway where no turning movement restriction is required.
  - (2) Commercial two-way entrances are acceptable along a divided highway only if there is an approved full-movement median opening at the site access.
  - (3) Where a formerly-undivided highway has been divided with the construction of a raised median, a commercial right-in/right-out entrance is to be used instead.
  - (4) All commercial entrances shall be channelized with the appropriate type of curb and gutter, determined in 5.9 Curb-and-Gutter, Medians, and Traffic Control Islands.
  - (5) Refer to the typical detail in Standard Entrance and Street Connection Details.
2.1.3 Commercial One-Way Entrances
- 2.1.3.A. Description – Commercial one-way entrances allow for inbound or outbound movement between curbed sides.
- 2.1.3.B. Applications
  - (1) Commercial one-way entrances are appropriate where it is desirable to isolate inbound and outbound movements along the site frontage, in consideration of site circulation, or to restrict movements along the state highway(s) to inbound or outbound only at one or more access points.
  - (2) Commercial one-way entrances may be used along a divided highway where necessary for site circulation. An appropriate skewed alignment is required to facilitate easy right turns in or out, as applicable.
  - (3) All commercial entrances shall be channelized with the appropriate type of curb and gutter, determined in 5.9 Curb-and-Gutter, Medians, and Traffic Control Islands .
  - (4) Refer to the typical detail in Standard Entrance and Street Connection Details.
2.1.4 Commercial Right-In/Right-Out Entrances
- 2.1.4.A. Description – Commercial right-in/right-out entrances provide separate driveways dedicated to inbound and outbound right-turn movements at a single access point. A raised island separates the movements to provide directional control.
- 2.1.4.B. Applications
  - (1) Commercial right-in/right-out entrances shall be used on all divided highways with posted speeds above 40 mph. Alternatively, in urban street environments where posted speeds are 40 mph or lower and a narrow raised median separates the directional highways, other commercial entrances may be used as long as appropriate signing is provided to discourage errant movements.
  - (2) The standard layout, with 17' or 20' track widths as appropriate for the design vehicle, shall be used.
  - (3) In rare instances, a right-in/right-out entrance may be required along an undivided highway. This is generally for the purpose of controlling left turns or in anticipation of future construction of a divided highway.
  - (4) Commercial right-in/right-out entrances shall be fully channelized along both sides of the inbound and outbound movements. Channelization shall extend from the right-of-way line or back of sidewalk to the normal frontage curb along the highway.
  - (5) Commercial right-in/right-out entrances shall have a raised channelization island acceptable to MDOT SHA. For applications along undivided highways, the channelization island shall be extended in accordance with the standard for this purpose or as acceptable to MDOT SHA.
  - (6) Refer to the typical detail in Standard Entrance and Street Connection Details.
2.1.5 Monumental Entrances
- 2.1.5.A. Description – Monumental entrances include a raised median that separates inbound and outbound movements and extends for a considerable distance away from the highway into the site. Monumental entrances may be designed for multiple lanes, full movement, right-in/right-out, or other restricted access.
- 2.1.5.B. Applications
  - (1) The use of monumental entrances will generally be reserved for access to large commercial and industrial sites where there is a need to separate and define multi-lane inbound and outbound traffic movements. The typical application involves a signalized intersection at the state highway.
  - (2) Monumental entrances are ideally suited to applications in which a significant throat length, as defined in 2.4.4 Connection Depth/Throat Length, is required to avoid on-site traffic conflicts near the highway access point.
  - (3) Monumental entrances shall be centered directly opposite from existing or proposed monumental entrances and public streets, in as much as possible, to minimize the lane shift required for vehicles crossing the intersection.
  - (4) Lane shift, if applicable, at 4-leg intersections formed by the access point shall be evaluated using MUTCD criteria.
2.1.6 Special Entrance Designs – Special design entrances are permitted for instances in which a specialized entrance design may be appropriate to address unusual site-generated traffic or field conditions. All special entrance designs are subject to review and approval by MDOT SHA and will not be considered unless need is clearly demonstrated.

2.2 Horizontal Layout

The horizontal layout of entrances shall comply with the following standards:

2.2.1 Width of Connection
- (1) Entrance width shall be measured perpendicular to the centerline of the entrance.
- (2) The maximum width for a two-way entrance shall be 35’. The minimum width of a two-way access is 25’.
- (3) The maximum width for a one-way entrance shall be 20’. The minimum width shall be 17’.
- (4) Right-in/right-out entrances shall conform to MDOT SHA standards with a one-way width of 20’ where commercial vehicles are anticipated and 17’ where predominantly passenger vehicles are anticipated. Compact right-in/right-out entrances with a minimum one-way width of 14’ may be permitted where acceptable to the SHA.
- (5) Exceptions based on traffic, type of access, site circulation, type or size of using vehicles, or existing conditions may be considered by MDOT SHA.
2.2.2 Angle of Connection
- (1) The angle of connection for two-way entrances shall be between 70 and 110 degrees, measured as the angle between the centerline of the entrance and the centerline of the state highway.
- (2) The angle of connection for one-way entrances shall be between 45 and 90 degrees, measured as the angle between the centerline of the entrance and the centerline of the state highway.
- (3) If the state highway is in a horizontal curve, the angle of connection shall be measured as the angle between the centerline of the entrance and a tangent to the curve at the intersection point of the entrance centerline and the highway centerline.
2.2.3 Entrance Intersection Radius and Flare
- (1) Typical minimum intersection radius for a Standard Channelized Entrance is 30'.
- (2) Minimum radii for other types of channelized entrances are identified in the pertinent entrance standard.
- (3) The intersection radius required for a specific entrance shall be as appropriate for the design vehicle. The entrance shall be designed so that the design vehicle does not have to encroach into adjacent travel lanes to use the entrance.
- (4) Depressed curb entrances shall have flares conforming to the pertinent entrance standard.
2.2.4 Traffic Control Islands and Medians
- (1) Traffic control islands within entrances shall consist of the appropriate type of Standard Curb and Gutter, set back from the roadway and nosed down.
- (2) All traffic control islands shall have a minimum of 75 square feet of surface area enclosed.
- (3) Medians 6’ wide or less shall consist of Standard Monolithic Median. The nose of the median shall be set back from the roadway and nosed down.
- (4) Medians greater than 6’ wide shall utilize the appropriate type of Standard Curb and Gutter.

2.3 Vertical Layout

The vertical layout of entrances shall comply with the following standards.

2.3.1 Maximum Grade – The profile grades of commercial entrances should be as flat as possible on those sections that are to be used for storage space for stopped vehicles. Grade limitations are as follows:
- (1) Grades in excess of 3% may not be allowed on the landing grade (first 40’) of entrances, unless otherwise approved by MDOT SHA.
- (2) Grades beyond the landing grade shall be in accordance with currently accepted engineering practices, but may not exceed 6% for a distance of 40’ and not exceed 8% beyond that distance.
- (3) The use of vertical curves is recommended to maintain the required entrance grades.
- (4) For sites smaller than ½ acre with low traffic generation rates, the landing grades may not exceed 6% for a minimum length of 40’.
2.3.2 Grade Breaks – The maximum grade break allowed between the state highway pavement and the entrance profile grade is 8%. This applies to normal crowned and superelevated state highway conditions. The use of vertical curves is recommended to provide a smooth transition.
2.3.3 Grading and Drainage Provisions – The profile grade lines and cross sections on the entrances shall be designed to provide a smooth junction and proper drainage. The entrance cross section at the intersection with the road edge shall be controlled by the highway profile grades.
2.3.4 Entrance Profile – Whenever required by MDOT SHA, a profile of any entrance proposed for use shall be provided on the plans submitted for review and approval. The existing and proposed profile grades along the centerline of the entrance shall be shown extending from the highway centerline into the site for a distance sufficient to demonstrate compliance. All grades, elevations, offsets, flow lines, grade breaks, and controls shall be clearly labeled and drawn to scale.

2.4 Site Plan Coordination

Various site plan elements can have a substantial effect on the operation of highway access points. Careful attention to these factors reduces vehicular conflicts in the entrance areas.

2.4.1 Site Circulation – When developing the site plan, every effort should be made to employ accepted traffic engineering principles in designing an interior traffic pattern that supports proper entrance operation without stacking of vehicles onto the highway.
2.4.2 Setbacks and Building Restrictions – In order for the entrances to operate at maximum efficiency, it is recommended that the minimum desirable building setback line be 30’ from the right-of-way line or limits of dedication. Building setback lines are subject to the regulations of the pertinent local government approving authority.
2.4.3 Pump Island Location – In order for the entrances to operate at maximum efficiency, it is recommended that the roadside face of the pump island of fueling stations be set a minimum of 12’, preferably 15’, from the property line. Pump setback lines are subject to the regulations of the pertinent local government approving authority.

2.4.4 Connection Depth/Throat Length – Throat length is measured from the proposed edge of the highway to the first on-site intersection or vehicular conflict point. The edge of the highway shall be determined based on the ultimate highway typical section, where future widening is anticipated.

2.4.4.A. The minimum throat lengths in Table 2.4.4 shall be provided where feasible and reasonable, as determined by MDOT SHA, for the principal site access point(s). Additional length may be appropriate for primary highways and other high-volume, high-speed arterial routes.
2.4.4.B. A queuing analysis may be required to determine the necessary throat length for larger commercial sites. The required length may be governed by queuing of inbound and/or outbound vehicles.
2.4.4.C. Traffic entering larger commercial sites shall be given right-of-way at the intersection(s) with drive aisles through appropriate signing and pavement markings.
2.4.4.D. The minimum acceptable throat length for commercial entrances under any circumstances shall be adequate to establish the standard entrance layout. For example, an entrance with a 30' radius implies at least a 30' throat length. An entrance with a 10' radius implies at least a 10' throat length.
2.4.4.E. Entrance throats shall be continuous, with no intersecting drive aisles, for the specified length.
2.4.4.F. Where site conditions preclude construction of the normally required deceleration lane, additional throat length may be required to assure satisfactory operation of the access point without stacking of vehicles into the state highway.

Table 2.4.4 Minimum Throat Length for Commercial/Industrial Entrances

Type of Development	Min. Throat Length (ft)
Regional Shopping Malls	250
Community Shopping Center (supermarket, drug store, other stores)	120
Small Strip Shopping Center	30
Regional Office Park	250
Office Building/Professional Center	80
Small Commercial Development Sites	30