Notes for Chapter 8 Roadway DesignBridge Railings Purpose: prevent vehicles from running off the edge ofbridges or culverts.CE222 Highway EngineeringNotes for Chapter 8 Roadway Design1. Roadway EnvironmentRun-Off-Road accidents are subjected to the use of restraint systems by vehicles occupants, type of vehicle and the nature of the roadside environment. Highway designers ---- roadway environment2. Clear Roadway Recovery AreasGenerally speaking, 30 ft from the traveled way (85percent of the vehicles run off the roads can avoid accidents. Detail clear zone distances need to be calculated using Table 8-1( meters) on page 224 or Table 8-1a (feet) on page 669.3. Figure 8-2. Understand three concepts:Recoverable slopes 4: 1 or flatterNon-recoverable slopes 3:1 to 4:1Critical slopes: 3:1 or steeper4. Ditches and Drainage StructuresDitches: Learn the use of Figure 8-3 and Figure 8-4Drainage structures: Curbs, Cross-Drains and parallel drainage structures5. Breakaway sign and luminaire supportsBreakaway support: all types of sign, luminaire, and traffic signal supports that are designed to break or yield when struck by a vehicle.6. Longitudinal Barriers:Purposes: Prevent vehicles from leaving the roadway and crashing into roadside obstacles, overturning, or crossing into the path of vehicles traveling in theopposite direction.Classes: Roadside barriers, median barriers, and bridge barriersRoadside barriers: Flexible, semi-rigid, and rigid systemsGuardrail (flexible and semi-rigid category) Warrants for guardrail installationLateral Placement of barriers:Calculation of Length of barrier: See Figure 8-9 and Equation 8-1End Treatments: see Figure 8-10Median barriers:Warrants: ADT > 20,000 and median widths narrower than 30 ftSpecific locations with high potential accidentsTypes: NJ barriers and General BarrierBridge Railings Purpose: prevent vehicles from running off the edge of bridges or culverts.Types: relating to design speed, traffic volume, and the truck and bus portion in the traffic stream7. Crush cushions Placement Locations:Retaining walls, bridge piers, abutments and off-ramp gore areasDesign:Kinetic energy principle and the conservation of momentum principle Discuss Example 8-1 (Kinetic energy principle) andExample 8-2 (momentum principle)HOMEWORK: Problems 8-1, 8-3 and