Engineering and Aesthetics Session 3

Engineering vs. Aesthetics Source: City of Bellevue, “Speed Hump: Design, Pavement Marking, and Signing”

Design of Horizontal Measures R = V 2 /15(e+f) R = radius of a horizontal measure (ft) V = speed of travel through the measure (mph) e = superelevation rate of road f = side friction factor

Mean Operating Speed Posted Speed Limit Critical Point Design Speed AASHTO Design Speed ALIGNMENT TangentCurveTangent Curve Design, Operating, & Posted Speeds

Desired Speed Assumed Side Friction 1 Assumed Superelevation Maximum Radius  15 mph    Based on American Association of State Highway and Transportation Officials (AASHTO), A Policy on Geometric Design of Highways and Streets, Washington, D.C., 1990, Figure III- 17 and Table III-17. Maximum Curve Radii for Various Desired Speeds

Another Constraint -- Long Wheelbase Vehicles Source: KPG, Inc., Design Report for SE 46th Way Traffic Control Improvements, City of Bellevue, WA, 1994.

Under and Over Designed Horizontal Measures

Design of Vertical Measures A = 2.15V 2 /R R = V 2 /5.81 A = acceleration (ft/sec 2 ) V = speed of travel over a vertical measure (mph) R = radius of the measure (ft)

Under- and Overdesigned Vertical Measures

Aesthetics -- With and Without Landscaping

Landscaping Policies AgencyNeighborhood Dayton, OHinstallmaintain Eugene, ORinstallmaintain till volunteer dies/moves Gainesville, FLinstallmaintain choose plants from city nursery Montgomery Co. installmaintain choose landscape palette San Diego, CA installmaintain choose plants from approved list Tallahassee, FL install & maintain reconsidering because of “uglies” Howard Co., MDinstall & maintain

Limited Guidance for Traffic Calming

Result -- Lack of Universal Recognition

Result -- Political Controversy

One Model of Standardization -- Australia

Another Model of Standardization -- Maryland

Need for Context Sensitivity

MUTCD General Guidance... engineering judgment is essential to the proper use of signs, the same as with other traffic control devices Information of a less important nature and extraneous information should be moved to less critical locations or deleted A conservative use of regulatory and warning signs is recommended as these signs, if used to excess, tend to lose their effectiveness In situations where messages are required other than those herein provided for, the signs shall be the same shape and color as standard signs of the same functional type

MUTCD Operational Guidance  Yellow diamond-shaped signs for warning  Yellow lines separating opposing traffic  Lettering or symbols of adequate size  Short legends  Symbols in preference to word messages  Educational plaques with new specialty signs  Advance warning when high driver judgment or deceleration to a specific speed is required  Size, height, position, lettering, and reflectorization per MUTCD

Applications of MUTCD Signs

Specialty Signs