designing for older drivers - texas a&m university · designing for older drivers marcus a....
TRANSCRIPT
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