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FHWA Home / Safety / Road Diets (Roadway Reconfiguration) / Road Diet Informational Guide

Road Diet Informational Guide

Appendix B – Feasibility Determination Factors, Characteristics, and Sample Evaluative Questions

Factor Characteristics Sample Evaluative Questions
Roadway Function and
Environment
  • Actual, Expected, and Desired Primary Function (Access, Mobility, or a Combination of the Two)
  • Community Objectives or Goals for the Roadway
  • Available Right-of-Way
  • Current and Expected Adjacent Land Use
  • Jurisdictional Plan or Policy for Conversions
  • Jurisdictional Context Sensitive or Complete Street Policy
  • What is the primary current, expected, and desired function of the roadway?
  • Is the roadway primarily a collector or minor arterial roadway?
  • Does the current roadway primarily operate as a "de facto" three-lane cross section?
  • Is the goal for the roadway improvement increased safety with somewhat lower mobility?
  • Is the right-of-way limited?
  • Will the adjacent land use remain relatively stable throughout the design period?
  • Will the proposed cross section match the desired function of the roadway?
  • Will the answers to the above questions remain the same throughout the design period of the project?
  • Does the jurisdiction have a plan or policy related to these types of conversions?
  • Does the jurisdiction have a context sensitive or Complete Streets policy that may apply?
Crash Types and Patterns
  • Type of Crashes
  • Location of Crashes
  • Number and Location of Pedestrians and Bicyclists
  • Parallel Parking  Needs
  • Can the crashes that are occurring be reduced with a conversion?
  • Will a reduction in speed and speed variability increase safety?
  • Are there safety concerns related to parallel parking maneuvers?
  • Do pedestrians and bicyclists have safety concerns?
Pedestrian and Bike Activity
  • Number and Location of Pedestrians
  • Number and Location of Bicyclist Use
  • Characteristics of Pedestrians and Bicyclists (e.g., Age)
  • Bicycle and Pedestrian Friendliness of Roadway
  • Cross-section Width
  • Parallel Parking Need
  • Bus Stop Locations
  • What is the pedestrian and bicyclist friendliness of the roadway?
  • Do pedestrians and bicyclists have safety concerns?
  • Will the addition of a TWLTL assist pedestrians and bicyclists?
  • How  will pedestrians and bicyclists interact with parallel parking?
  • Can a bike lane be added after the conversion?
Overall Traffic Volume and Level of Service
  • Total Daily Volume
  • Peak-Hour Volume (Morning/Noon/Evening)
  • Directional Split
  • Intersection and Arterial Level of Service
  • Side Street and Driveway Vehicle Delay
  • Volume of Frequent-Stop or Slow-MovingVehicles
  • Vehicle  Classification
  • Signal Timing or Phasing
  • Arterial Travel Speeds and Vehicle Delays
  • Existence of Turn Lanes
  • What is an acceptable increase in minor street or signal- related delay due to the conversion?
  • Is a decrease in arterial travel speed of 5 mph or less acceptable?
  • What is an acceptable reduction in intersection level of service?
  • What level of daily traffic volume and peak hour exists or is expected in the design year?
  • Does the signal timing or phasing need to be changed?
  • Does the current roadway primarily operate as a "de facto" three-lane cross section?
  • What is the potential impact during off-peak hours?
Turning Volumes and Patterns
  • Number and Location of Turn Volumes and Access Points
  • Peak Time Period of Turn Volumes
  • Existence of Left-Turn and Right-Turn Lanes
  • Design of Access Points and Intersections
  • Turn Volume of Frequent-Stop or Slow- Moving Vehicles
  • Minor  Street and Access Point Vehicle Delay
  • Signal Timing or Phasing
  • Does the signal timing or phasing need to be changed or optimized?
  • How important is it that right-turning vehicles quickly enter or exit the roadway?
  • Do the access point and intersections need to be redesigned (e.g., radii, approach slopes, location)?
  • Are right-turn lanes needed at particular locations?
  • Does the proposed marking allow the design vehicle (e.g., tractor-trailer) to turn properly?
  • What is an acceptable increase in minor street vehicle delay and left-turning vehicle delay?
  • Does the current roadway primarily operate as a "de facto" three-lane cross section?
Frequent-Stop and/or
Slow-Moving Vehicles
  • Volume, Location, and Time of Frequent-Stop and/or Slow-Moving Vehicles
  • Type, Design (Length, Width, Turning Radius, etc.) and Speed of Vehicles
  • Arterial Travel Speeds and Vehicle Delays
  • Level of Enforcement for Proper TWLTL Use (i.e., No Passing Allowed)
  • What is the acceptable delay with respect to frequent- stop and/or slow-moving vehicles?
  • Can these vehicles turn properly at the access points and intersections?
  • Can passing  prohibitions be feasibly enforced?
  • Are there locations for pull-outs for these vehicles?
  • Can some or all of the stop locations for the frequent-stop vehicles be combined?
  • What are the potential peak and off-peak impacts?
Weaving, Speed, and
Queues
  • Signal Timing or Phasing
  • Number  of Existing Lane Changes
  • Turn Volume and Location
  • Arterial Travel Speeds and Vehicle Delays
  • Level of Enforcement for Proper TWLTL Use (i.e., No Passing Allowed)
  • Number  and Location of Turn Volumes and Access Points
  • Peak Time Period of Turn Volumes
  • Existence of Left-Turn and Right-Turn Lanes
  • Design of Access Points and Intersections
  • Turn Volume of Frequent-Stop or Slow- Moving Vehicles
  • Minor  Street and Access Point Vehicle Delay
  • Queue Length
  • Number  of Speeders
  • Does the signal timing or phasing need to be changed or optimized?
  • How important is it that right-turning vehicles quickly enter or exit the roadway?
  • Do the access point and intersections need to be redesigned (e.g., radii, approach slopes, location)?
  • Are right-turn lanes needed at particular locations?
  • What is an acceptable increase in minor street and left- turning vehicle delay?
  • Is a decrease in arterial travel speed of 5 miles per hour or less acceptable?
  • What is an acceptable change in queues?
  • Are there safety concerns related to weaving?
  • Can no passing be enforced?
  • Can drivers  be educated about proper use of TWLTL?
  • Is a reduction in speeders and speed variability preferred?
  • Can all the old markings be completely removed?
  • Does the current roadway primarily operate as a "de facto" three-lane cross section?
Right-of-Way Availability, Cost, and Acquisition Impacts
  • Available Right-of-Way
  • Cost of Right-of-Way
  • Existence of Left-Turn and Right-Turn Lanes
  • Design of Access Points and Intersections
  • Number  of Properties Needed and Environmental Impacts (e.g., Tree Removal)
  • Cross Section Width
  • Parallel Parking  Needs
  • Is the right-of-way limited?
  • Will the cost of right-of-way acquisition be significant?
  • Do the access point and intersections need to be redesigned (e.g., radii, approach slopes, location)?
  • Are right-turn lanes needed at particular locations?
  • What is necessary in the cross section (e.g., bike lane, parallel parking, etc.)?
General Characteristics
Parallel Roadways
  • Roadway Network Layout
  • Volume and Characteristics of Through Vehicles Diverted
  • Impact of Diversion on Parallel Roadways
  • Is a decrease in arterial travel speed of 5 miles per hour or less acceptable?
  • Does the signal timing or phasing need to change or be optimized?
  • Will conversion divert through vehicles to parallel roadways?
  • Is it possible to avoid or reroute the diverted traffic?
  • What is the impact on the parallel roadway environment?
Offset Minor Street
Intersections
  • Volume and Time of Left Turns
  • Queue Lengths
  • Distance between Minor Street Approaches
  • Do left turns occur into both minor street and access point approaches at a similar time?
  • Are the left-turn volumes significant?
  • Will the left-turn volumes produce queues in the through lanes of a three-lane roadway?
Parallel Parking
  • Parallel Parking  Needs
  • Number  of Parking Maneuvers
  • Operational and Safety Impacts of Parallel Parking
  • Design of Existing or Proposed Parallel Parking
  • Does parallel parking exist?
  • How many parking maneuvers occur during peak travel times?
  • What are the safety and delay concerns related to parallel parking maneuvers?
  • Is it possible to design these spaces for easy entry or exit (i.e., to minimize delay)?
  • Will it be necessary to reduce the number of parking spaces?
  • Does parallel parking reduce the ability of vehicles to turn in and out of minor streets and access points?
Corner Radii
  • Design of Access Points and Intersections
  • Number  and Location of Turn Volumes and Access Points
  • Peak Time Period of Turn Volumes
  • Existence of Left-Turn and Right-Turn Lanes
  • Turn Volume of Frequent-Stop or Slow- Moving Vehicles
  • Minor  Street and Access Point Vehicle Delay
  • How important is it that right-turning vehicles quickly enter or exit the roadway?
  • Do the access points and intersections need to be redesigned (e.g., radii, approach slopes, location)?
  • Are right-turn lanes needed at particular locations?
  • Does the proposed marking allow the design vehicle (e.g., tractor-trailer) to turn properly?
  • Do parallel parking spaces need to be removed to allow proper turning?
At-Grade Railroad
Crossing
  • Volume, Location, and Time of Train Crossing
  • Length of Crossing Train
  • Delay  Impacts of Train Crossing
  • Queue Impacts of Train Crossing
  • Total Daily Vehicle Volume
  • Peak-Hour Vehicle Volume  (Morning/Noon/ Evening)
  • Directional Split of Vehicles
  • Do trains cross during peak travel periods?
  • What is the typical delay from a train crossing?
  • Is double the current queue length (with four-lane undivided cross section) at a railroad at-grade crossing acceptable?
  • Is there a nearby parallel at-grade intersection where impacts may need to be mitigated?

Adapted from Knapp, Welch, and Witmer, 1999.


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Page last modified on November 24, 2014.
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Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000