chapter9 - Warrants As part of an express highway system...

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CE222 Highway Engineering Notes for Chapter 9 Intersections, Interchanges, and Terminals 1. Intersections at Grade, Grade Separations, and Interchanges Intersections at grade Types: Three-Approach, Four-Approach, and Four-More Approach (see Figure 9-1 on Page 247) Design Factors: Design speed: 10 mph Design vehicle: assumed design vehicles Curb line: turning path of the largest class of vehicles Radius: 25-30 ft (Detail see Tables 9-1, 9-2) Three-centered curves or Simple Curve with taper (Draw a diagram to students) Island and Channels Advantages Separation of conflicts Control of angle of conflict Reduction of excessive pavement areas Regulation of traffic flow in the intersection area Arrangement for predominant turning movement Protection of peds Protection and storage of turning and crossing vehicle Location of traffic control devices Types: Directional or channelized, divisional and refuge AASHTO: > 75 ft*ft and 100 ft*ft preferable > 12 ft for each side > 4 ft wide, 20-25 ft long 2. Grade Separations and Interchanges
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Unformatted text preview: Warrants: As part of an express highway system designed to carry volumes of traffic To eliminate bottlenecks To prevent accidents Where the volume to be catered for would require the design of an intersection at grade of unreasonable size Where the road user benefit of reducing delays at an at-grade intersection > improvement cost Types T and Y interchanges: Trumpet for solving left turn on the freeway Diamond Interchanges Partial and full cloverleafs Directional Interchanges 3. Design of Ramps and Turning Roadways See Caltrans design manual in terms of maximum grade, minimum radius of ramp curve, width and exit and entrance connection to freeway. 4. Railroad Grade Intersections Warrants: All mainline railroads (two or more trucks /single line tracks with six or more trains per day. 5. Design of Parking Facilities Will be discussed in CE223. Here forget it. Homework: 1) Why is the interchange design B (figure 9-8) better than design A (figure 9-8)?...
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