Method for computing an energy efficient route
View Patent ↗Probe data is analyzed to derive Longitudinal Speed Profiles (LSPs) and an Optimal Longitudinal Speed Profile ( 18 ) for each road segment or link in a digital map network. The Longitudinal Speed Profiles (LSPs) profiles are calculated during defined time spans whereas the Optimal Longitudinal Speed Profile ( 18 ) is based on the LSP for the time span corresponding only to free flow traffic conditions. All of the LSPs can used to create a respective energy cost for each time span, or only the OLSP ( 18 ) can be used (or alternatively the RRDSL 16 or LRRDSL 17 ) to calculate an energy cost for the free flow conditions only. The energy cost can be used to predict the energy required by a vehicle to traverse the link. Navigation software can use the energy cost to plan the most energy efficient route between two locations in the digital map. Sensory signals can be activated if a driver strays from the Optimal Longitudinal Speed Profile ( 18 ) to achieve extremely high levels of energy efficiency.
1. A method for creating Longitudinal Speed Profile (LSP) data, said method comprising the steps of:
collecting probe data from a plurality of probes traversing a road segment in the form of vehicular traffic flow, each probe developing a respective probe trace comprising a sequence of discrete time-stamped probe positions;
establishing daily time spans;
bundling probe data recorded during each time span;
statistically deriving Longitudinal Speed Profiles (LSPs) from the bundled probe data, the Longitudinal Speed Profiles (LSPs) describing the speed variations along the road segment during the respective time spans;
associating the Longitudinal Speed Profiles (LSPs) with the road segment; and
storing the Longitudinal Speed Profiles (LSPs) in a digital medium;
said method further comprising the steps of:
utilizing the Longitudinal Speed Profiles (LSPs) data to calculate by a processor an energy cost for a direction of travel supported by the link; and
associating the energy cost with the road segment.
2. The method according to claim 1 wherein said step of statistically deriving Longitudinal Speed Profiles (LSPs) includes determining a given Longitudinal Speed Profile (LSP) individually per direction of travel along the associated road section.
3. The method according to claim 2 wherein said step of statistically deriving Longitudinal Speed Profiles (LSPs) includes determining a given Longitudinal Speed Profile (LSP) individually per driving lane of the associated road section.
4. The method according to claim 1 wherein said step of bundling probe data includes deriving at least one vehicle category-specific Longitudinal Speed Profile (LSP).
5. The method according to claim 1 further including the step of providing a digital map having at least one link corresponding to the road segment; and said step of storing the Longitudinal Speed Profiles (LSPs) including augmenting the digital map with a data layer containing the stored Longitudinal Speed Profiles (LSPs).
6. The method according to claim 1 wherein the digital map includes a network of links extending between an origin location and a destination location, calculating an energy cost for each link in the network, and further including the step of planning a route between the origin and the destination by analyzing the energy cost for alternative links in the network and preferring those links which minimize the energy cost.
7. The method according to claim 1 wherein said step of calculating an energy cost for the link includes adding the number of top and/or minimum speed peaks on that link.
8. The method according to claim 1 wherein said step of creating an energy cost includes at least one of: (i) taking the first derivative of speed over time as derived from the probe data; (ii) taking the probe data itself which already contains measured speed and/or acceleration values from specific sensors; (iii) quantifying the area enclosed by the speed-times-acceleration function, both for the area with positive and with negative acceleration; (iv) deriving at least one vehicle category-specific energy cost from probe data bundled by that vehicle category; (v) calculating an aerodynamic resistance, the energy cost being proportional to the aerodynamic resistance; (vi) calculating a rolling resistance, the energy cost being proportional to the rolling resistance; (vii) calculating a gradient, the energy cost being proportional to the gradient.
9. The method according to claim 1 wherein said step of establishing daily time spans includes at least one of: (i) creating unique time spans for each day of the week; and (ii) creating unique time spans for national holidays.
10. A method for computing an energy efficient route between an origin location and a destination location in a digital map, said method comprising the steps of:
providing a digital map having a plurality of road segments represented therein by a network of links corresponding to road sections in reality supporting vehicular travel in at least one direction, the links extending between an origin location and a destination location;
collecting probe data from a plurality of probes traversing the links, each probe developing a respective probe trace comprising a sequence of discrete time-stamped probe positions;
establishing daily time spans;
bundling probe data recorded for each link during each time span;
statistically deriving Longitudinal Speed Profiles (LSPs) from the bundled probe data, the Longitudinal Speed Profiles (LSPs) describing the speed variations along the road segment during the respective time spans;
utilizing the Longitudinal Speed Profiles (LSPs) during at least one time span to calculate by a processor an energy cost for the direction of travel supported by the link;
planning a route between the origin and the destination by analyzing the energy cost for alternative link combinations in the network and preferring those links which minimize the energy cost.
11. The method of claim 10 further including the step of associating each energy cost to the respective link as an attribute in the digital map.