Generating segment data

1. A method of generating and using segment data for a segment of an electronic map, the electronic map being representative of a network in an area covered by the electronic map and comprising a plurality of segments, each segment representing a navigable segment of the network, the method comprising using a processing apparatus to:

collect historic travel data for the segment of the electronic map relating to the movement of a plurality of navigation devices along the navigable segment of the network represented by the segment, and using the historic travel data to generate a plurality of speeds of travel across the segment;

generate a free-flow speed for the segment using at least some of the plurality speeds of travel, wherein said free-flow speed is an average speed of travel across the segment during a period of time in which there is no or substantially little traffic on the navigable segment of the network;

define a jam condition for the segment, such that where the jam condition is satisfied the segment is classified as jammed and otherwise as not jammed, the jam condition being a jam threshold speed, wherein the jam threshold speed is a selected percentage of the free-flow speed for the segment;

generate a jam probability for the segment, wherein the jam probability is representative of the likelihood of a jam on the navigable segment represented by the segment, and wherein the jam probability is calculated based on a ratio of speeds of travel across the segment above the jam threshold speed to speeds of travel across the segment below the jam threshold speed;

generate a jam speed for the segment using at least some of the plurality of speeds of travel, the jam speed being indicative of the speed on the segment when the segment is classified as jammed, wherein the jam speed is a selected percentage or mode of speeds of travel across the segment below the jam threshold speed;

associate the jam probability and the jam speed with the segment in the electronic map, the segment data for the segment comprising the jam probability and the jam speed; and

use at least the segment data for the segment to at least one of: generate and provide a route across the electronic map; and determine and/or predict the existence of a jam on a navigable segment of the network and issue a jam warning.

2. A method according to claim 1 where the selected percentage of the free-flow speed is between 30% and 70%.

3. A method according to claim 1 where the historic travel data is grouped according to time of recordal allowing the generation of multiple time dependent jam probabilities for the segment.

4. A method according to claim 3 where jam probabilities are calculated according to or are at least influenced by one or more of: (i) the time of the year; (ii) the day of the week; (iii) the time of day; and (iv) the occurrence of a particular event or situation.

5. A method according to claim 1 where the jam speed is the average of substantially all speeds of travel across the segment below the jam threshold speed.

6. A method according to claim 1 where the speeds of travel across the segment form a multi-modal distribution, and the jam speed is a lower mode of the distribution.

7. A system arranged to generate and use segment data for a segment of an electronic map, the electronic map being representative of a network in an area covered by the electronic map and comprising a plurality of segments, each segment representing a navigable segment of the network, the system comprising: a processor; and a memory coupled to the processor, and the system being arranged to:

collect historic travel data for the segment of the electronic map relating to the movement of a plurality of navigation devices along the navigable segment of the network represented by the segment, and using the historic travel data to generate a plurality of speeds of travel across the segment;

generate a free-flow speed for the segment at at least some of the plurality speeds of travel, wherein said free-flow speed is an average speed of travel across the segment during a period of time in which there is no or substantially little traffic on the navigable segment of the network;

define a jam condition for the segment, such that where the jam condition is satisfied the segment is classified as jammed and otherwise as not jammed, the jam condition being a jam threshold speed, wherein the jam threshold speed is a selected percentage of the free-flow speed for the segment;

generate a jam probability for the segment, wherein the jam probability is representative of the likelihood of a jam on the navigable segment represented by the segment, and wherein the jam probability is calculated based on a ratio of speeds of travel across the segment above the jam threshold speed to speeds of travel across the segment below the jam threshold speed;

generate a jam speed for the segment using at least some of the plurality of speeds of travel, the jam speed being indicative of the speed on the segment when the segment is classified as jammed, wherein the jam speed is a selected percentage or mode of speeds of travel across the segment below the jam threshold speed;

associate the jam probability and the jam speed with the segment in the electronic map, the segment data for the segment comprising the jam probability and the jam speed; and

use at least the segment data for the segment to at least one of: generate and provide a route across the electronic map; and determine or predict the existence of a jam on a navigable segment of the network and issue a jam warning.

8. A non-transitory computer readable medium comprising instructions which, when executed by a computer, cause the computer to perform a method of generating and using segment data for a segment of an electronic map, the electronic map being representative of a network in an area covered by the electronic map and comprising a plurality of segments, each segment representing a navigable segment of the network, the method comprising:

collecting historic travel data for the segment of the electronic map relating to the movement of a plurality of navigation devices along the navigable segment of the network represented by the segment, and using the historic travel data to generate a plurality of speeds of travel across the segment;

generating a free-flow speed for the segment at at least some of the plurality speeds of travel, wherein said free-flow speed is an average speed of travel across the segment during a period of time in which there is no or substantially little traffic on the navigable segment of the network;

defining a jam condition for the segment, such that where the jam condition is satisfied the segment is classified as jammed and otherwise as not jammed, the jam condition being a jam threshold speed, wherein the jam threshold speed is a selected percentage of the free-flow speed for the segment;

generating a jam probability for the segment, wherein the jam probability is representative of indicating the likelihood of a jam on the navigable segment represented by the segment, and wherein the jam probability is calculated based on a ratio of speeds of travel across the segment above the jam threshold speed to speeds of travel across the segment below the jam threshold speed;

generating a jam speed for the segment using at least some of the plurality of speeds of travel, the jam speed being indicative of the speed on the segment when the segment is classified as jammed, wherein the jam speed is a selected percentage or mode of speeds of travel across the segment below the jam threshold speed;

associating the jam probability and the jam speed with the segment in the electronic map, the segment data for the segment comprising the jam probability and the jam speed; and

using at least the segment data for the segment to at least one of: generate and provide a route across the electronic map; and determine or predict the existence of a jam on a navigable segment of the network and issue a jam warning.

9. A method according to claim 1 where the selected percentage of the free-flow speed is between 40% and 60%.

10. A method according to claim 1 where the selected percentage of the free-flow speed is substantially 50%.