List of Figures

Figure 1	Comparison of nominal and substantive concepts of safety
Figure 2	NCHRP Report 500 series
Figure 3	Steps in the design exception process
Figure 4	Advanced technology is making the collection of in-service data more effective and more efficient
Figure 5	Because it is a design control, design speed affects the curvature, stopping sight distance, superelevation, and other features of this horizontal curve
Figure 6	Accident Modification Factors for lane width on rural two-lane highways
Figure 7	Shoulders on this urban freeway provide enough width for crash avoidance, storage of disabled vehicles, maintenance activities, and enforcement
Figure 8	Partially-paved shoulders on this rural arterial improve bicycle accommodation and reduce risky passing maneuvers
Figure 9	Pavement edge drop-off
Figure 10	Comparison of how shoulder width affects stopping sight distance past concrete bridge rail along horizontal curves
Figure 11	Accident Modification Factors for shoulder width on rural two-lane highways
Figure 12	Bridge width
Figure 13	Vehicle shying towards the centerline on a narrow bridge
Figure 14	Horizontal alignment
Figure 15	Superelevation
Figure 16	Horizontal curve at the base of a steep grade
Figure 17	Vertical stopping sight distance at a crest vertical curve
Figure 18	Headlight sight distance at a sag vertical curve
Figure 19	Sight distance at an undercrossing
Figure 20	Horizontal stopping sight distance
Figure 21	Not all locations with limited stopping sight distance are the same in terms of safety risk
Figure 22	Stopping sight distance profile
Figure 23	Cross-slope break on the high side of a superelevated curve
Figure 24	Interstate closure after an impact with a bridge
Figure 25	Lateral offset to obstruction is an operational offset and is not the same as clear zone
Figure 26	Signs can be used to warn drivers in advance of a change in lane width
Figure 27	Wide pavement markings
Figure 28	Recessed pavement markings
Figure 29	Raised pavement markings
Figure 30	Post-mounted delineators
Figure 31	Lighting
Figure 32	Shoulder rumble strips
Figure 33	Centerline rumble strips
Figure 34	Painted edgeline rumble strips
Figure 35	Partially paved shoulders
Figure 36	Safety edge (top) and after the shoulder has been graded over the edge (bottom)
Figure 37	Fixed object removal. Separate box culverts were extended, connected, and covered at this interchange
Figure 38	Breakaway light poles
Figure 39	Shielding fixed objects with barrier
Figure 40	Pull-off area on the inside of a horizontal curve
Figure 41	Signs can be used to warn drivers in advance of a narrow bridge
Figure 42	Reflector tabs on guardrail
Figure 43	Object markers and post-mounted delineators at a narrow bridge
Figure 44	White concrete bridge rail
Figure 45	Anti-icing system on a bridge
Figure 46	Bridge rail and guardrail transition in compliance with NCHRP Report 350
Figure 47	Turn warning sign with flashing beacon
Figure 48	Curve warning sign.
Figure 49	Dynamic curve warning system
Figure 50	Delineation with large chevrons
Figure 51	Delineation with post-mounted delineators
Figure 52	Delineations with reflectors on barrier
Figure 53	Advance warning of a steep grade
Figure 54	Climbing lane
Figure 55	Truck escape ramp
Figure 56	Continuous drainage system
Figure 57	Sign for crest vertical curve with inadequate stopping sight distance
Figure 58	Intersection warning sign with flashers activated by vehicles entering from the side road
Figure 59	A STOP sign with a flashing beacon improves visibility of the sign at this intersection with limited vertical sight distance
Figure 60	Intersection lighting
Figure 61	SLIPPERY WHEN WET sign
Figure 62	Longitudinal texture applied to fresh pavement to improve surface friction
Figure 63	Transverse grooving to improve surface drainage and friction
Figure 64	An example of transitioning the cross slope of the shoulder to mitigate a cross-slope break greater than 8%
Figure 65	Vertical clearance signing
Figure 66	Vertical clearance signing
Figure 67	Warning sign with hanging chimes installed at the same height as the vertical clearance of the structure
Figure 68	Reflective sheeting on utility poles
Figure 69	Reflective sheeting on utility poles
Figure 70	The project runs through Des Moines, Iowa
Figure 71	Approximate project limits of design exception
Figure 72	Interstate 235 before reconstruction
Figure 73	Interstate 235 after reconstruction
Figure 74	Cross section within the unconstrained locations
Figure 75	The unconstrained cross section
Figure 76	Cross section within the area of restricted width
Figure 77	Narrower lane widths would place the lane lines in a different transverse position than the underlying longitudinal joints
Figure 78	Inside lane and shoulder widths within the constrained areas were narrowed
Figure 79	Lighting was placed on the outside of the freeway through the design exception area
Figure 80	Lighting was placed down the center of the median where more cross-sectional width was available
Figure 81	The project is located in north-central Wyoming
Figure 82	Approximate project limits
Figure 83	The steep cut on the north side of the highway and deep canyon on the south illustrate the difficult terrain faced by designers
Figure 84	The Tensleep-Buffalo Highway leads into the Big Horn National Forest in the Rocky Mountains
Figure 85	A massive retaining wall illustrates the difficult site constraints that were encountered
Figure 86	Signing for the steep grades is provided throughout the project
Figure 87	Electronic signing provides enhanced warning for the non-standard horizontal curves
Figure 88	Advance signing for the truck escape ramp
Figure 89	Advance signing for the brake-check turnout
Figure 90	A pull-off area provides tourist information and spectacular views
Figure 91	Runaway truck ramp with arrestor system
Figure 92	Runaway truck ramp
Figure 93	Electronic signing provides advance warning when the truck ramp is closed
Figure 94	Climbing lane
Figure 95	Guardrail on the outside of a horizontal curve
Figure 96	State Route 99 is an urban arterial in Seattle, Washington
Figure 97	State Route 99 parallels Interstate 5 through the Seattle metro area
Figure 98	SR 99 before and after reconstruction in Des Moines
Figure 99	SR 99 before and after reconstruction in SeaTac (top) and Shoreline (bottom)
Figure 100	Drawing of proposed improvements to SR 99 in Shoreline
Figure 101	Left-turn lane and U-turn areas after reconstruction in Federal Way
Figure 102	New transit stop in Des Moines
Figure 103	SR 99 before and after reconstruction in Des Moines
Figure 104	Median tree plantings along SR 99 in SeaTac
Figure 105	Impact with tree in median (SeaTac)
Figure 106	Information from City maintenance personnel provided data on tree impacts that were not reported
Figure 107	When the in-service evaluation showed that many tree hits were occurring at the narrow-median locations adjacent to turn lanes, trees were no longer planted in these areas in subsequent phases of the project (SeaTac)
Figure 108	A low-profile barrier was used along the median of SR 99 in Des Moines.
Figure 109	Sloped-down end section adjacent to turn lane
Figure 110	Two low-profile barriers have passed NCHRP Report 350 test-level 2 (45 mph) crash testing
Figure 111	Los Angeles, California
Figure 112	State Route 110. The Arroyo Seco Parkway
Figure 113	SR 110 shortly after construction in 1940
Figure 114	Historic structures along the Arroyo Seco Parkway
Figure 115	The San Gabriel Mountains on the horizon illustrate the Parkways scenic context
Figure 116	The Arroyo Seco Parkway has a narrow cross section, a curvilinear alignment, and non-standard interchange geometry
Figure 117	The Arroyo Seco Channel runs adjacent to the Parkway, constraining its width on one side
Figure 118	Single-slope concrete median barrier at a horizontal curve
Figure 119	Pull-off areas provided periodically along the outside lanes
Figure 120	Enhanced delineation with raised pavement markers and pavement markings with high retroreflectivity
Figure 121	Warning signs for curvature, slowing traffic, and vertical clearance
Figure 122	Geometry at the State Street Exit Ramp

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