AM13-09(B): Weaving in the Vicinity of an Approach

Type: Bulletin

Topic or Program: Access Management  |  Vehicle Weaving

Final Number: AM13-09(B)

Effective Date: 05/15/2013

Updated Date: 04/04/2022

Signature on File: Angela Kargel, Access Management Program Manager

This Technical Services Bulletin provides guidance for understanding and applying OAR 734-051-4020 (3)(f) to existing connections and applications for new highway approaches. This guidance will help achieve greater statewide consistency in evaluating connections and approach applications for safety and operations concerns related to vehicle weaving in the vicinity of an intersection.

Approach

A legally constructed public or private connection to the highway that provides vehicular access to or from a state highway as defined in OAR 734-051-1070(9)(s)-(c).

Connection

An existing approach as defined in OAR 734-051-1070(9) or an unpermitted means of vehicular access to or from a state highway and an abutting private property, city street or county road. (OAR 734-051-1070(14))

OAR

Oregon Administrative Rule.

ORS

Oregon Revised Statute.

Peak Hour

The highest one-hour volume observed on an urban roadway during a typical or average week, or the thirtieth (30th) highest hourly traffic volume on a rural roadway typically observed during a year.

Weaving

The movements that vehicles make when exiting an approach and then maneuvering across travel lanes to position the vehicle in the proper lane to make a turn at a downstream intersection or ramp.

This guidance is for use by the department’s Access Management staff and may be shared with members of the public. The guidance is for use as a screening level assessment of potential weaving concerns. No traffic analysis is required for this review. Permit Specialists should coordinate with Access Management staff to confirm their evaluation is consistent with this guidance.

It is important to note that no weaving analysis is needed on two-lane highways when the following conditions apply: total two-way AADT is less than 5,000, approach ADT is less than or equal to 400, and crash rate is below 120 percent of the statewide crash rate.

Attachment A, Weaving Distance for Approach Permitting, provides specific details on data collection and general guidance in applying traffic engineering principles for use in determining potential weaving problems. There are two weave distance criteria, minimum and desirable. Adequacy of weave distance may be based on the minimum distance if speed and volume levels are below recommended thresholds. If thresholds are exceeded, adequacy is based on the desirable distance.

ODOT staff performing a more detailed review for the approach application should be familiar with the Analysis Procedures Manual (APM) section 4.8.1 on Functional Area of an Intersection. This section includes procedures for identifying the factors impacting the approach location. The APM is available online at http://www.oregon.gov/ODOT/Planning/Pages/APM.aspx

During 2011, ODOT revised the criteria it uses to evaluate safety and operations issues when permitting a highway approach. Six explicit criteria were added to Division 51, including how to evaluate weaving issues in the vicinity of certain intersections. OAR 734-051-4020(3)(f) reads:

“3. Safety and Operations Concerns. The department has the burden of proving any safety or highway operations concerns relied upon in the department’s decision to require mitigation when it approves an application with mitigation or to deny an application. The department may deny an application where the applicant is unable to provide adequate improvements to mitigate documented safety or highway operations concerns and is required pursuant to OAR 734-051-3070. Safety or highway operations concerns that may be considered by the department are limited to (a) through (f):

(f) Insufficient distance for weave movements made by vehicles exiting the proposed approach across multiple lanes in the vicinity of:

(A) Signalized intersections; or
(B) Roads classified as collectors or arterials; or
(C) On-ramps or off-ramps.”

The primary purpose of the safety and operations concerns listed in OAR 734-051-4020(3) is to ensure that key safety and operational elements of a proposed approach are evaluated during the decision to approve, approve with mitigation, or deny an approach application. The evaluation of these concerns typically determines the location and mitigation requirements associated with approval of an approach application and may identify a significant safety problem that the applicant cannot or is unwilling to mitigate, resulting in ODOT’s denial of the approach application.

ODOT staff are expected to work with the applicant to the extent possible to solve problems identified during the evaluation of safety factors, recognizing that the problems and solutions must be viewed in the context of practical design and balanced against other important considerations, including local community or government aspirations and economic development.

As indicated in OAR 734-051-4020(3), the department is responsible for proving that unique safety and highway operations concerns exist at or near the location of a proposed approach. This can be accomplished by observation, evaluation and review of existing records for the location of concern. Where potential issues are identified, data and analysis may also be needed. If a Traffic Impact Analysis (TIA) is required pursuant with OAR 734-051-3030(4), the TIA shall be scoped to include a safety and operations analysis per OAR 734-051-3030(5)(d) and the analysis must be sufficient to allow the department to assess safety and operational impacts.

Weaving, for the purposes of this Bulletin, occurs when vehicles exiting an approach must maneuver across travel lanes in order to turn from or exit the highway at a downstream intersection or ramp. Approaches that are located where sufficient distance for weaving maneuvers is not available can contribute to high speed differentials, violation of traffic laws, abrupt stops, and diagonal maneuvers across lanes, leading to increased crash potential and degraded intersection operations.

Assuming measurements indicate the potential for concerns with weaving, the Permit Specialist or individual taking measurements should involve a staff member experienced in engineering analysis to determine if the concern is significant. This evaluation would be site specific but could include traffic counts and other information necessary to confirm the issues associated with the location. It is important to distinguish between how 734-051-4020(3) factors and design standards are used in the permitting process. Generally, the factors identified in 4020(3) are used in the process to identify where a problem exists or is expected to develop in association with an approach or where the approach could possibly exacerbate conditions.

Design standards are applied after approval of the approach application and during the development of the construction plans and specifications. Design standards are contained in various manuals and technical publications, such as the Highway Design Manual. Design standards are used to prepare construction plans and details (i.e., approach width, length of turn lanes, surfacing, etc.). It should be recognized that there is a correlation between the factors and design standards. They are not totally distinct from one another. For example, sight distance must be considered during the design of an approach or if the approach can only be approved as a right-in/right-out, the design of restricting the approach to a right-in/right-out must be evaluated. In some cases, it may be necessary to do some level of design prior to approval of an approach so as to understand how the approach will impact highway features or operations, site circulation or other important considerations. Generally speaking, 734-051-4020(3) factors are applied prior to approval of an application to determine if an approach can be approved at a specific location.

Department staff members in the following positions are responsible for carrying out the guidance in this Bulletin as it relates to their assigned duties and authority:

• Region Managers.
• District Managers.
• Region Access Management Engineers.
• Development Review Coordinators.
• Access Management Coordinators.
• Permit Specialists.

Implement this Bulletin upon the effective date.

If problems develop while implementing this guidance or further clarification is needed, contact the Access Management Program Manager.