Designing for Older Drivers Marcus A. Brewer, P.E., PMP October 10, 2017 Transportation Short Course Design Session
Designing for Older Drivers
Marcus A. Brewer, P.E., PMP
October 10, 2017
Transportation Short Course
Design Session
Acknowledgements
• Authors:
– Marcus Brewer, Debbie Murillo (TTI)
– Alan Pate (Battelle)
• Authors of previous draft:
– David Harkey, Raghavan Srinivasan, et al. (HSRC)
– Loren Staplin, Kathy Lococo (TransAnalytics)
– Hugh McGee, Michael Tantillo (VHB)
Acknowledgements
• FHWA Government Task Manager (GTM):– Rebecca Crowe
• FHWA reviewers and contributors:– Gene Amparano, FHWA Resource Center
– Mark Doctor, FHWA Resource Center
– Keith Harrison, FHWA Resource Center
– Ken Kochevar, FHWA California Division
– Fred Ranck, formerly FHWA Resource Center
– Dick Schaffer, formerly FHWA Office of Safety
– Scott Wainwright, formerly FHWA Office of Operations
– Kevin Sylvester, FHWA Office of Operations, MUTCD Team
How to Obtain the Handbook
• Electronic copy:
– http://safety.fhwa.dot.gov/older_users
– PDF and HTML versions
• Printed copy:
– Can be ordered from FHWA Office of Safety
Background
• Increase in aging persons in the population and as road users
• Steadily increasing proportion of drivers and pedestrians with declining abilities to:
– See and hear
– Walk or operate a vehicle
– Process information and make decisions
Older Drivers in Texas
Image Credit: Texas Strategic Highway Safety Plan
Older Drivers in Texas
• According to SHSP, from 2010-2015:
– Males 75+ and females 80+ overrepresented in crashes based on miles driven
– Steady increase in crash rates for older drivers
– Older drivers more likely to have angle, same-direction, and opposite-direction crashes; less likely to have single-vehicle crashes
Older Drivers in Texas
Number Strategy
1 Reduce wrong way crashes
2 Design and operate roadways to meet the needs of older road users
3 Implement effective methods and tools to prepare older road users to deal with the limitations brought on by the aging process
4 Improve mobility options for older road users
5 Implement methods to reduce injury severity among older road users
NOTE: All older road users strategies and countermeasures should consider the needs of persons with disabilities.
SHSP strategies for Older Road Users:
21 countermeasures and programs supporting those strategies
Older Drivers in Texas
Number Strategy
1 Reduce wrong way crashes
2 Design and operate roadways to meet the needs of older road users
3 Implement effective methods and tools to prepare older road users to deal with the limitations brought on by the aging process
4 Improve mobility options for older road users
5 Implement methods to reduce injury severity among older road users
NOTE: All older road users strategies and countermeasures should consider the needs of persons with disabilities.
SHSP strategies for Older Road Users:
5 design-related countermeasures, including use of Handbook
Overview – Handbook Content
• Current Handbook is third edition in series
• Key changes
– New title: Handbook for Designing Roadways for the Aging Population
– Inclusion of newer research
– True HTML version in addition to print and PDF
Overview – Handbook Content
• Similar layout to previous edition
– Front matter and Chapter 1: introduction, overview, and worksheets
– Part I (Chapters 2-6): treatments & recommendations
– Part II (Chapters 7-11): rationale & supporting evidence
– Appendices: tech notes, visibility, glossary, references
• Similar focus on five categories of treatments
Part I – Treatments
Category Proven Practices
Promising Practices
Total Treatments
Intersections 16 8 24
Interchanges 6 2 8
Roadway Segments 4 6 10
Work Zones 5 2 7
Highway-Rail Grade Crossings 2 0 2
Total 33 18 51
Chapter 2 – Intersections
• Intersection Sight Distance
– Gap of no less than 8.0 s, plus 0.5 s for each additional lane crossed, for ISD calculations
• Offset Left-Turn Lanes
– Recommended positive offset of at least 4 ft for passenger cars, 5.5 ft if designing for heavy trucks
Chapter 2 – Intersections
• Offset Left-Turn Lanes (cont.)
– Minimum offset distances recommended for specific design speeds
– Signs and markings to supplement design
Chapter 2 – Intersections
• Channelization
– Raised channelization with sloping curbs for left-and right-turn lane treatments less than 45 mph
– Retroreflective markings for horizontal and vertical curb surfaces of raised channelization
– Acceleration lane provided for channelized right turns for speeds of 45 mph or greater
– Pedestrian refuge provided with channelization treatments
– Raised medians preferred over TWLTL
Chapter 2 – Intersections
• Delineation of Edge Lines and Curbs
– Maintain minimum in-service luminance contrast level between marked edge of roadway and the road surface (2.0 with lighting, 3.0 without)
– Delineate curbs (vertical face and portion of top surface) with markings and optional signs/object markers
Image Credit: David Harkey, Highway Safety Resource Center, University of North Carolina
Chapter 2 – Intersections
• Left-Turn Traffic Control for Signalized Intersections
– Recommend protected-only wherever appropriate
– Use R10-12 sign with permissive green ball
– Optional advance signing
– Lead phasing preferred over lag phasing
Image Credit: Marcus Brewer, Texas A&M Transportation Institute
Chapter 2 – Intersections
• Street Name Signs
– Minimum letter heights for ground-mounted
– Overhead signs supplement at major intersections (uppercase 12 in; lowercase 9 in)
– Advance street name plaque used with advance intersection warning sign or traffic control sign
– Advance street name signs
– Retroreflective sheeting
Posted speed < 25 mph
Posted speed > 25 mph
Uppercase 6.0 in 8.0 in
Lowercase 4.5 in 6.0 in
Chapter 2 – Intersections
• Stop and Yield Signs
– Standard sizes required by MUTCD
– Minimum retroreflectivity levels
– Supplemental warning sign for two-way stop
– Stop Ahead sign placement
– Retroreflective sheeting
– Transverse markings
Single lane Multi-lane Freeway
STOP 30 in 36 in --
YIELD 36 in 48 in 60 in
Chapter 2 – Intersections
• Lane Assignment on Intersection Approach
– Lane-use control signs (R3-5 and R3-6 series) on mast arm
– Advance (5 s) use of R3 signs and pavement markings
Chapter 2 – Promising Practices
• Right-Turn Channelization Design
– Radii for turning speeds of 17-18 mph and optimize line of sight for turning drivers
Chapter 2 – Intersections
• Pedestrian Crossings
– Use walking speed of 3 ft/s and measure crossing distance to begin 6 ft behind curb
– With channelized right-turn lanes, refuge island conforming to AASHTO and MUTCD, and marked crosswalk one car length from yield line
Chapter 2 – Promising Practices
• Combination Lane-Use/Destination Overhead Guide Signs
– Provide additional guidance at intersections with complex design features or heavy traffic
Chapter 2 – Promising Practices
• Signal Head Visibility
– One signal head per lane, centered over each lane
– Shared signal for left turns if using green ball, or separate signal using flashing yellow arrow
Image Credit: Marcus Brewer, Texas A&M Transportation Institute
Chapter 3 – Promising Practices
• Wrong-Way Driving Countermeasures
– Additional treatments to counter wrong-way driving by aging drivers (e.g., improved lighting, channelization, signs, and markings)
– Road Safety Audit to examine performance and determine appropriate countermeasures
Conclusion
The Handbook for Designing Roadways for the Aging Population provides an update to a long-standing FHWA resource to help practitioners consider older road users in their designs.
While the Handbook does not constitute a standard, it does provide a wide range of recommendations and references on treatments to consider.
Thank you for attending!
• Marcus A. Brewer, P.E., PMP
• Handbook
• Desk Reference (NEW!)
• and other resources– http://safety.fhwa.dot.gov/older_users
• Texas Strategic Highway Safety Plan– https://www.texasshsp.com