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Operational and “Vehicular” Characteristics. Dr. Wen Cheng, P.E., T.E., PTOE June 24 th , 2010 Cal Poly Pomona. Learning Objectives. Highway vehicle characteristics Highway traffic stream characteristics Air vehicle characteristics Waterborne Vessels Characteristics
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Operational and “Vehicular” Characteristics Dr. Wen Cheng, P.E., T.E., PTOE June 24th, 2010 Cal Poly Pomona
Learning Objectives • Highway vehicle characteristics • Highway traffic stream characteristics • Air vehicle characteristics • Waterborne Vessels Characteristics • Railway vehicles-related characteristics • Train resistance calculation
Mode selection Mode choice= f (safety, convenience, price, speed, capacity) • Capacity vs. Speed • Low speed, low capacity • High speed, low capacity • Our goal is high speed, high capacity
Energy consumption of transport The U.S. is an extremely mobile society. Transportation: 2/3 of petroleum, 27.5% of total energy.
Vehicle characteristics • Dimension • Width • Length • Height • Weight • Operating characteristics • Acceleration rate • Deceleration rate • Etc. • Design vehicle: selected to represent all vehicles on the highway. It is typically the largest vehicle likely to use the highway with considerable frequency. • AASHTO has designated 15 design vehicles (P, BUS, P/B, etc.)
How to determine the design vehicle One road section example • Obtain the existing road use data • Predict the proportions of various vehicle types • Select the design vehicles (accommodation vs. economy) , usu. should be greater than 2% of the traffic volume
Traffic stream characteristics • Speed • Volume • Density • Time headway • Space headway
Travel Speed Definition: Total distance traversed divided by the travel time Units: (m/s; ft/s; mph; km/h)
Three Types of Travel Speeds • Spot Speed (instantaneous speed) • Relatively short distance • Measured by laser, radar, camera, or manually by stop watch • Running Speed • Relatively long distance • Travel time: motion time only, stop-delay time excluded • Overall Speed • Relatively long distance • Travel time: motion time + stop-delay time
Dash-mounted radar Hand-heldlaser Camera Stop Watch
Two Types of Avg. Spot Speeds Time-mean Speed Space-mean Speed Relationship:
Traffic Volume Definition: The number of vehicles that pass a roadway point per unit of time Units: (veh/day; veh/hr; veh/min; etc.)
Volume-Measuring Devices Video Detector Loop Detector Tube Detector Hand-held collector
Four Major Types of Travel Volumes • AADT (Annual Avg. Daily Traffic: veh/day) • Avg. # over a period of 365 days • ADT (Avg. Daily Traffic: veh/day) • Avg. # over a period less than 365 days • DHV (Design Hourly Volume: veh/hr) • Usu. 30th highest hourly volume of the design yr. • DHV=AADT(or ADT)*k • DDHV (Directional Design Hourly Volume: veh/hr) • DDHV=AADT(or ADT)*D*k
Rate of Flow vs. Hourly Volume Rate of Flow Properties • Used to account for variability or peaking that may occur within 1 hr. • Each 15-min has its own rate of flow. • The peak 15-min volume is V15, peak rate of flow =4*V15
Peak Hour Factor (PHF) PHF=Hourly volume/peak rate of flow=V/(4*V15) Typical value: 0.88 (rural)~0.92 (urban) Q: In what situation PHF would be 1? Numerical Example
Time Headway (ht) • Definition: The time between the arrival of successive vehicles at a specified roadway point. • Avg. ht is the reciprocal of volume, if expressed in secs/veh, then:
Traffic Density • Definition: The avg. # of vehicles occupying a unit length of roadway at a given instant. • Units: veh/mi; veh/km; veh/mi/ln; veh/km/ln • It is hard tophysically measure, but it can be calculated as:
Space Headway (hs) • Definition: The distance between successive vehicles, typically measured from front bumper to front bumper. • Avg. hs is the reciprocal of density, if expressed in ft/veh, then:
Summary of various relationships Vf, V0, s, a, t Speed, density, volume Volume, time headway Density, space headway
Various transport aircrafts Boeing 707 (1950’s) Boeing 787 (2007) Airbus A-300 (1970’s) DC-9 (1980’S)
STOL (short takeoff or landing) aircraft General aviation aircraft
Aircraft characteristics and their effects • Dimension (fuselage length, wingspan, deck height, etc.) • Design of parking area • Runway and taxiway width • Turning radii • Hangars and maintenance sheds • Weight • Pavement thickness for runways, taxiways, aprons • Capacity • Terminal size • Baggage-handling facilities • Departure lounge • Gate positions • Fuel storage • Range • Frequency of operations, mix of type, and size of aircraft
Trends of aircraft characteristics • Weight: continuing growth from 1930 to present • Note: due to elaborate landing gears, there is no similar increased thickness of airfield pavements • Fuselage length: grew steadily since 1945 • Note: aircraft most likely will approach a ceiling on length as designs with_______are introduced • Wing span: has increased only slightly • Note: great news, as aprons, hangars, etc. are slightly affected • Cruising speed: 190mph (1930’s) to 1800 mph (present) • Note: increased speed give steadily decreasing marginal returns in savings of travel time (benefits vs. costs) • Runway length: due to turbofan engine, the trend of increased runway length might stop. • Passenger capacity: increase significantly • Great news or bad news?
Passenger ship General cargo carrier Tanker carrier Inland waterway barge
Shipping types Definition Tanker service: designed for carriage of bulk liquid cargoes. Liner service: relatively frequent sailings with definite and advertised schedule Nonliner service: special sailings without predetermined or fixed schedule
Freight car types Covered hopper hopper Auto rack car Tank car
Freight car types (cont’d) Flatcar Gondola Containers Boxcar
Passenger train types and characteristics • Intercity • Hold sustained speeds for relatively long time • Urban rail transit • Accelerate and decelerate constantly • Scenic tour • Recreation purpose • High speed rail (HSR) • Acela, U.S.A. • Tgv, Europe • Bullet Train, Japan • Meglev, China
Level tangent resistance AAR formula