1. (a)

   1. (1) Once the safety analysis is complete in the purpose and need, safety issues and considerations in the evaluation of conceptual design alternatives should be identified.
   2. (2) The IJR should demonstrate that the proposed alternatives will not have significant or adverse impact on the safe operation of the freeway system.
   3. (3) The IJR should also identify any design features that may result in a higher risk of safety impacts.
   4. (4) Figure 6 shows a table of safety impacts of not implementing certain design features.

2. (b)

   1. (1) Some safety impacts of alternatives are highly dependent on traffic forecasts, such as inadequate turn lane storage or inadequate weaving length.
   2. (2) It is therefore crucial that a sensitivity analysis, as outlined in 27 CAR § 95-401 et seq., should be considered to determine the risk of such impacts.
   3. (3) Conflict areas with significant traffic volumes on the crossroad (such as busy driveways near the ramp terminal intersection) or on the freeway main lanes (such as closely spaced ramps), particularly that can result in a high speed differential, should be identified and considered in the analysis.

      Geometric Feature	Operational Effect	Safety Impact
      Lack of route continuity	Excessive lane changingViolate driver expectationsIncreased signing requirements	Moderate
      No lane continuity (basic lanes)	Excessive lane changing	Moderate
      No lane balance (exit entrances)	Increased lane changing	Moderate
      Inadequate application of auxiliary lanes	Capacity reductionIncreased lane changing	Moderate
      Left exits/entrances	Increased lane changingTwo-sided weaving (across all lanes)Increased signing requirements	High
      Two exits/interchanges	Increased signing requirementsPotential driver confusion	Moderate
      Exit beyond crossroad	Reduce exit visibilityDriver comfort/convenience	Moderate
      Inadequate exit/entrance designShort taper/parallelSmall radius at exit/entrance gore	Inadequate merge/diverge opportunitiesInadequate speed for entering vehiclesExiting vehicles slow on main lanes-speed differential	Moderate
      Inadequate exit ramp length	Queuing onto main lanes	High
      Inadequate weaving sectionsShort weaving sectionTwo-sided weaving section	Capacity reductionExcessive lane changingLane changing across all lanesSpeed differential between vehicles-all lanes	High
      Inadequate decision sight distance	Driver confusion/indecisionDriver comfort/convenience	Moderate

      Source: Freeway and Interchange Geometric Design Handbook, 2005, ITE Figure 6. Freeway and Interchange Geometric Features Impacting Operations and Safety

3. (c)

   1. (1) Other safety impacts of alternatives are highly dependent on geometric design, such as the use of a low-speed exit loop ramp that may meet geometric standards but may not be consistent with driver expectations.
   2. (2) Any design exceptions for any alternative that may have a safety impact should be identified in the IJR.

4. (d)

   1. (1) Currently, there is little in the way of widely accepted safety guidance and tools available for agencies to use in the analysis of safety performance of highways.
   2. (2) As a result, safety considerations often carry little weight in the project development process.
   3. (3) However, with continued emphasis being placed on reducing the numbers of fatal and serious crashes on the highway system, new approaches and tools for the quantitative analysis of safety performance are being developed.
   4. (4) For instance, two (2) new tools for the analysis of safety performance that will have a large impact on the development of highway projects will be the Highway Safety Manual and the Interchange Safety Analysis Tool.
   5. (5) The Federal Highway Administration Interstate System Access Informational Guide provides additional guidance regarding safety analyses that may be appropriate in an IJR.

Codification Notes: “IJR” means Interchange Justification Report.