fall 2014. many elderly live in poverty, ill health, and inadequate housing increasingly, many of...
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Designing for Older Drivers
Fall 2014
Many elderly live in poverty, ill health, and inadequate housing
Increasingly, many of those over age 65 will be very old—over age 80–85. In the United States, the number of those over age 85 grew 300% between 1960 and 1996—to 3.8 million people, comprising 1% of the U.S.
By the middle of the next century, 1 in 20 Americans will be over age 85
Women live longer than men (more female drivers)
Recent Trends
See also:◦ Understanding Older Drivers: An Examination of
Medical Conditions, Medication Use, and Travel Behavior by AAA (2014) (https://www.aaafoundation.org/sites/default/files/Medication%20and%20Travel%20Behaviors%20--%20FINAL%20FTS%20FORMAT%20copy.pdf)
◦ Millennials in Motion: Changing Travel Habits of Young Americans and the Implications for Public Policy (Oct. 2014) (http://www.uspirg.org/sites/pirg/files/reports/Millennials%20in%20Motion%20USPIRG.pdf) (http://www.uspirg.org/reports/usp/millennials-motion)
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Designing for Older Drivers
Values can be used for computing the sight distance at intersections
Designing for Older Drivers
Designing for Older Drivers
Designing for Older Drivers
Intersection DesignRecommended Design: Skewed Intersection
● In the design of a new facility (or re-design), all intersecting highways should meet at 90o
● If ROW is restrictive, the skew angle should be no less than 75o
● If skewed angle smaller, a RTOR prohibition is recommended
Intersection DesignRecommended Design: Receiving Lane Width
● 12-ft lane and 4-ft shoulder (critical task: lane positioning)
Recommended Design: Channelization
● Raised channelization with sloping curbs preferred over pavement markings
● Use retroreflectorized marking maintained at minimum luminance level
● provide acceleration lane for right-turn channelization
Recommended Design: Sight Distance Requirements
● PRT should be above 2.5 seconds for left, right and crossing
● Use a minimum of 8.0 seconds for a left-turn from a stopped maneuver
Intersection DesignRecommended Design: Left-Turn Geometry & Signing
● Provide positive offset design with unrestricted sight distance
● Use truck design templates whenever there is a high probability of truck traffic
● When positive offset design is not possible, provide adequate signing and pavement marking
Intersection Design
Intersection Design
Intersection Design
Intersection Design
Intersection DesignRecommended Design: Curb Radius
● 25 ft to 30 ft to minimize pedestrian crossing and moderate the speed of turning vehicles
Recommended Design: Traffic Control for Left-Turn Traffic
● Use separate signal heads
● Use protected-only signals whenever possible (leading rather than lagging)
● Install “LEFT-TURN YIELD ON GREEN” sign
● Green arrow followed by left arrow and then solid red circular red
Intersection DesignRecommended Design: Street Signs
● 6-in minimum size
● Use overhead-mounted street signs with mixed-case letters
● Use redundant street-name signs (not mandatory)
● If different street names, the names should be separated and accompanied by directional arrows
Intersection DesignRecommended Design: One-Way/Wrong-Way
Intersection DesignRecommended Design: One-Way/Wrong-Way
Intersection DesignRecommended Design: Stop Controlled
● Use supplemental sign under stop sign
Intersection DesignRecommended Design: Pedestrian Crossings
● Use 2.8 ft/s seconds walking speed
Where right-turn lane is channelized
Two-stage crossing (median refuge island)
Intersection DesignRecommended Design: Pedestrian Crossings
Curve Design
Interchange DesignRecommended Design: Exit Signing & Ramp Gore Design
● 1-in letter for every 33 ft distance
● Mixed-case font for overhead signs
Interchange DesignRecommended Design: Exit Signing & Ramp Gore Design
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