Basic concepts

Basic concepts - Basic Principles of Intersection...

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1 Basic Principles of Intersection Signalization Hong K LO Civil Engineering HKUST
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2 Types of Intersections • Intersection at grade • Grade separation without ramps • Interchanges: rely on geometry to avoid conflicts, for high volumes and safety; high cost
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4 Design considerations and objectives The objective is to reduce severity of potential conflicts between vehicles (pedestrians) while providing maximum convenience and ease of movement to vehicles. 4 basic elements for designing at-grade intersections: human factors: driving habits and decision and reaction times traffic conditions: capacities and turning movements, vehicle speeds, and size and distribution of vehicles physical elements, e.g., characteristics and use of abutting property, sight distance and geometric features economic factors: cost and benefits and energy consumption
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5 Traffic control devices include signs, movable barriers, and signals. They can be used along or in combination. Their objective is to separate conflicting vehicle streams in time e.g. stop sign, 4-way stop sign Traffic signs and markings are used to establish a street or highway system that is clearly understood by its users: drivers and pedestrians. They fulfill these purposes: traffic regulation (e.g., speed limit), turn prohibition, alerting, and warning drivers and pedestrians regarding roadway conditions, and guiding traffic along appropriate routes to reach trip destinations through signs and markings. different types of signs: regulatory signs - impose legal restrictions; warning signs - attention to hazardous conditions that otherwise not be readily apparent; guide or informational signs provide directions to drivers and to various destinations; directional signs used on highways at interchanges
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7 Types of intersection controls Stop signs are warranted: intersection of a less important road with a main road intersection of a county road, city street, or township road with a state highway street entering a through highway or street unsignalized intersection in a signalized area unsignalized intersection where a combination of high speed, restricted view, and serious accident record indicates a need for control •Y i e l d s i g n s : on a minor road at the entrance to an intersection when it is necessary to assign the right-of-way to the major road, but where a stop is not necessary at all times, and where the safe approach speed on the minor road exceeds 10 mph on the entrance ramp to an expressway, where an adequate acceleration lane is not provided Where there is a separate or channelized left-turn lane without an adequate acceleration lane at any intersection where a problem can be possibly corrected by a yield sign installation
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8 Types of intersection controls Intersection channelization channelization is the separation or regulation of conflicting traffic movements into definite paths of travel by traffic islands or pavement
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Basic concepts - Basic Principles of Intersection...

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