HighwayDesign Handbook

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Highway Design Handbook for Older Drivers and
Pedestrians
ENGINEERING COUNTERMEASURES to Accommodate Older
Drivers
March 28, 2008
Gene Amparano, P.E. Safety Engineer FHWA,
Resource Center
Publication No. FHWA-RD-01-103
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Engineering Countermeasures

• Strategies to Clarify and Simplify the Driving
  Task at
• Intersections
• Roadway Segments

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INTERSECTIONS

• Primary Goal is to Clarify and Simplify
• Signalized/ Unsignalized
• street name signs (location and size)
• location of signal heads
• lane control signs
• left-turns
• skew angle
• lighting
• roundabouts

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Street Name Signage larger and overhead
Redundant street name signs for major
intersections (midblock postings - overhead where
feasible) Use of directional arrows and
separated names at locations where the
intersecting roads have different names

• Minimum Letter Heights
• 300 mm (12 in) - Overhead

Over/under or on same line
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Street Name Signage advance notice
Provide advance street name sign
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Delineation Edge Treatments
Provide roadway edge (line or curb) maintain
with in-service contrast levels of a) 2.0 with
overhead lighting b) 3.0 without overhead lighting
Luminance Contrast (Lstripe -
Lpavement)/Lpavement
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Signal Head per Lane and Lane Control Signs
Signal Back Plates
consistent overhead placement of signal heads
and lane-use control signs
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Left-Turn Signalization
Protected-Only mode is recommended where 1)
capacity will permit, 2) minimum sight-distance
requirements cannot be met, 3) pattern of
left-turn crashes
protected-only operations
Provision of a separate signal face for the
left-turn lane is recommended to reduce driver
confusion
protected-permissive operations
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Offset Left-Turn Lane Geometry
Aligned
Positive Offset
Improved Line of Sight
Restricted Line of Sight
Positive offset

• Recommended Offsets
• 4 ft - passenger cars
• 6 ft - trucks

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Low Cost Positive Offset Treatment Left Turn Bay
Markings Arizona
12
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Left Turn Bay Markings to are angled from 12
to 10 to Improve Sight Distance
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Intersection Lighting Countermeasures
- Probe Lighting Design
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Intersecting Angle (Skew)
Unrestricted Right-of-Way
Restricted Right-of-Way
90o
gt 75o
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Essential roundabout characteristics
Slow speed entry
Slow speed exit
Splitter island
Truck apron
Crosswalk 1 car length back
Lots of deflection for slow speeds throughout
Separated sidewalk to direct peds to crosswalks
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ROADWAY SEGMENTS

• Primary Goal is to Clarify and Simplify
• Rural and Multilane Roadways
• Interchanges
• Signs (Size, Placement, font)
• Delineation
• Pavement Markings

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Larger Letter Size for Guide Signs
letter sizes based on 10 m (33 ft) legibility
distance per 25 mm (1 in) of letter height
Corresponds to 20/40 Vision accommodate greater
portion of older drivers
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InterchangesUse a parallel design for entrance
ramps
parallel design (preferred)
Gap search and acceptance area
tapered design
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Interchange Signing - diagrammatic signing
Existing MUTCD format
Recommended Alternative
number of arrow shafts matches number of lanes
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Michigan Side-by-Side Comparison
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Use Signs Larger than Minimum Requirements
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Street Name Signage advance notice
supplemental street name sign with advance
intersection warning sign
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Delineate Medians
Delineate the vertical face of curb and at least
a portion of the top surface
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Median Delineation
Painted Curb with reflectors mounted on top of
curb
Carson City, NV
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Curve Delineation Chevron Signs
Center sign aligned with drivers line of sight
Iowa
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Wider Pavement Edge Lines
Michigan DOT (2004) 6 edge lines
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Painting the rumbles freeway
Paint on rumble
Paint on pavement
Michigan pilot 100 freeway miles
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Engineering Countermeasures to Accommodate Older
Drivers
Thank You Gene Amparano, P.E. Safety
Engineer FHWA, Resource Center E-mail
gene.amparano_at_fhwa.dot.gov
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