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Method for Vehicle Routing and Traffic Management Disclosure Number: IPCOM000200544D
Publication Date: 2010-Oct-18
Document File: 3 page(s) / 26K

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Disclosed is a method for vehicle route planning as a function of aerodynamic profile.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 47% of the total text.

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Method for Vehicle Routing and Traffic Management

It is a mathematical certainty that the energy required to push an object through the air increases with the square of the speed. The energy expenditure is required to overcome the force of the fluid, gas or water, in which the object is moving. This force
is commonly referred to as "drag" and it is determined by three components; its speed; its face or the cross-sectional area it presents to the wind; and finally its drag coefficient. The drag coefficient --or Cd-- is a measure of the overall slipperiness of a vehicle's shape. As an example the Cd of a cube is about 2.1, a sphere is 0.5. Tractor trailers usually have a Cd between 0.7 and 0.9 while a typical car is between 0.25 and 0.35.

It is estimated that 60% of the total energy required to push the vehicle at highway speeds is used overcoming drag, while tire rolling resistance is about 25%. The remaining 15% is the effective work realized by the energy expenditure. Given that the majority of the energy used is expended in overcoming drag and that drag increases with the square of the speed which in turn is related to the vehicle's aerodynamic profile, as expressed by the Cd, it would be very beneficial to include the vehicle's Cd in vehicle route planning operations.

Mathematically speaking the effects of Cd can be neutralized by having a speed of zero. However in practicality this also results in zero movement of the vehicle. To change a vehicle's speed from a stand still the engine must chiefly overcome inertia. Inertia is the resistance of an object to change its state of motion and is directly related to the object's mass. Typical passenger vehicles have a GVWR (Gross Vehicle Weight Rating) of under 6,000 lbs, or about 2,700 Kg, while commercial semi-trailer trucks have a GVWR in excess of 26,000 lbr or more than 4 times that of passenger vehicles. It becomes clear then that the energy expenditure in overcoming inertia is variable by vehicle type. Since the "inertia tax" (the amount of energy required to overcome inertia) is paid only during the change in the state of motion, from "stopped" to "moving" or from "moving" to "stopped", it would be beneficial to include the vehicle's mass in route planning operations.

Current vehicle route planning operations include only time and distance variables and disregard vehicle type in performing calculations. Some more advanced implementations take into account known road limitations, such as local ordinances for truck routes in route planning operations.

To produce more accurate calculations, methods are needed to include vehicle type in route planning operations.

The disclosed invention consists of a method for vehicle route planning as a function of vehicle type, comprising:
• Providing a destination
• Determining a plurality of different routes for travel by a vehicle from a trip origin to the destination

• Identifying the vehicle according to its aerodynamic profile (e.g. g...