Technical Update

Corner Clearance Criteria

A PRIMER FOR LOCAL GOVERNMENT OFFICIALS AND EMPLOYEES AS THEY CONSIDER APPROVING SITE PLANS FOR PROPERTIES LOCATED ON OR NEAR A STREET CORNER

Corner clearances represent the  Frontage roads and connectors minimum distances that should be required between intersections and Inadequate corner clearances can driveways along arterial and collector result in traffic-operation, safety, and streets. As stated in AASHTO’s A Policy capacity problems. These problems on Geometric Design of Highways and can be caused by blocked driveway Streets: “Driveways should not be ingress and egress movements, situated within the functional conflicting and confusing turns at boundary of at-grade intersections. intersections, insufficient weaving This boundary would include the distances, and backups from far-side longitudinal limits of auxiliary lanes.” driveways into intersections. Also, Corner Clearance is discussed in FHWA’s Office of Operations website Specific operational and safety titled, “Access Management Principles problems include: Presentation”.  Through traffic is blocked by (http://ops.fhwa.dot.gov/access_mgm vehicles waiting to turn into a t/presentations/am_principles_intro/i driveway. ndex.htm) It is listed among the main  Right or left turns into or out of methods that are utilized as part of an a driveway (both on artery and agency’s Access Management crossroad) are blocked. Program. These methods include:  Driveway traffic is unable to  Permits, legislation, and corridor enter left-turn lanes. planning  Driveway exit movements are  Medians impacted by stopped vehicles in  Auxiliary lanes left-turn lanes.  Signals and signal spacing  Traffic entering an arterial road  Driveway location, spacing, and from the intersecting street or design road has insufficient distance.  Corner Clearance  The weaving maneuvers for  Cross-access and joint access vehicles turning onto an artery

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and then immediately turning maneuvers. left into a driveway are too  Driveways should be located as short. far from the intersection as  Confusion and conflicts resulting possible – either at or within 10 from dual interpretation of feet of the property line furthest right-turn signals. from the intersection.

Application Guidelines Actions vary for retrofits and new facilities. Corrective retrofit actions The following principles should guide include: corner clearance and driveway  Locating driveways at the planning: farthest edge of the property  Ideally, no driveways should be line from the intersection; permitted off of major highways  Consolidating driveways with (or major arterials). This adjacent properties, thereby requires safe and convenient increasing corner clearances; alternative access and  Closing driveways along the reasonable internal site arterial and requiring property circulation. access from the secondary road;  Where this is not possible, major and highways/arterials should have  Installing a raised median barrier physical (restrictive) medians to on approaches to intersections preclude left turns. Each corner to preclude left turns into or out parcel should have one driveway of a driveway. per roadway that is placed as far from the intersections as From a planning perspective, two possible. actions should be encouraged; both  Along undivided major require a proactive approach to highways/arterials, it is desirable corner clearances: to eliminate left-turn ingress  Establishing the desirable and egress at driveways within location of access points the “influence area” of an before property is subdivided intersection. This may entail or developed and providing short sections of a  Establishing minimum median divider and/or adopting requirements for property a driveway design that frontages in zoning and discourages or prevents left-turn subdivision regulations.

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Figure 1: Physical and Functional Areas of an Intersection.

Figure 2: Potential Access Points to Serve Corner Properties at the Intersection of Two Public Roads (very high number of conflict points).

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Figure 3: Potential Access Arrangement to Reduce the Number of Conflict Points for Properties Located at the Intersection of Two Public Roads. (The number of conflict points has been greatly reduced.)

Access Spacing for Major Arterials: Provide separation between access connections so that drivers can assess potential conflict locations one-at-a-time. Applicable spacing criteria may include:  Functional area  AASHTO stopping sight distance  Preventing right turn overlap (see below)  Other criteria as established by the Jurisdiction

Right turn overlap occurs when a through vehicle must monitor two egress right turning vehicles at once while still performing other driving tasks. By separating access points a proper distance, the overlap does not occur, and the through driver has only one egress right turning vehicle to monitor. Recommended minimum access spacings to avoid right turn overlap shown in Figure 4 are comparable to AASHTO stopping sight distances.

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Figure 4 - Minimum Access Spacing to Prevent Right Turn Overlap.

Speed Recommended Minimum Spacing ______(mph) (feet)______25 120 30 185 35 245 40 300 45 350 Intersection clearance should be the same as driveway spacings or at least as long as stopping sight distance. Source: Transportation Research Board Record 644 (1977).

Additional Access Spacing Considerations:  At a minimum, the upstream corner clearance should be longer than the longest expected queue at the adjacent intersection.  High speed, high volume roadways need longer corner clearances whereas the corner clearance on a local street can be much shorter.  Residential streets – driveways on corner lots should be located on the lesser street and near the property line most distant from the intersection.  Typically, all elements of an access drive, including the radii should be within a property frontage.  At a minimum, all driveway geometrics should be along the frontage of the property served by the driveway.  On major roadways, the corner clearance should be at least as long as the stopping sight distance so that vehicles turning corners can make safe stops when encountering entering traffic.  Encourage owners of adjacent properties to construct joint-use driveways in lieu of separate driveways.  Encourage a property owner to replace two or more driveways with a single driveway (or fewer driveways).  For adjacent properties, locate joint access on the property line. Reciprocal cross-access easement agreements must be executed.

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Notes

DISCLAIMER: This RON Technical Update is provided for purposes of general information only. This is not a primary technical or legal authority, and should not be relied upon as such. Interested persons should refer to the source documents referenced herein. Please note also that information contained in this document could become outdated or obsolete over time.

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