A device that estimates the travel speed of a mobile body obtains a speed similarity of a travel speed associated with a road subject to estimation and a travel speed associated with each section of a map. The device also obtains an environment similarity degree of environment information corresponding to a section including the subject road and environment information corresponding to each section. A section similar to the section including the subject road is selected based on the total similarity degree, which is calculated based on the speed similarity and the environment similarity, to set the travel speed associated with the selected section as a travel speed of a corresponding time period on the subject road.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A travel speed estimating device that estimates a travel speed of a mobile body, the travel speed estimating device comprising: a holding unit configured to hold map information, environment information associated with a map in the map information, and travel speed and time period that are associated with roads in the map information; a subject road specifying unit configured to specify a subject road, which is subject to travel speed estimation, from the roads in the map information; a dividing unit configured to divide the map in the map information into a plurality of sections; a speed similarity degree calculating unit configured to calculate a speed similarity degree, which is a similarity degree of the travel speed associated with the subject road and the travel speed associated with each of the plurality of sections; an environment similarity degree calculating unit configured to calculate an environment similarity degree, which is a similarity degree of the environment information corresponding to one of the plurality of sections including the subject road and the environment information corresponding to each of the plurality of sections; a total similarity degree calculating unit configured to calculate a total similarity degree for each of the plurality of sections based on the calculated speed similarity degree and the environment similarity degree; and an estimating unit configured to estimate the travel speed on the subject road when accumulation of the travel speed associated with the subject road is insufficient to estimate the travel speed on the subject road, wherein the estimating unit selects a section similar to the section including the subject road from the plurality of sections based on the total similarity degree, and the estimating unit sets the travel speed associated with the selected section as a travel speed of a corresponding time period on the subject road. 2. The travel speed estimating device according to claim 1, wherein the travel speed associated with each of the plurality of sections includes travel speeds respectively corresponding to a plurality of time periods, and the travel speed corresponding to each of the time periods is obtained by averaging speeds of a mobile body on a road included in each of the sections for each time period. 3. The travel speed estimating device according to claim 2, wherein the travel speed associated with the subject road includes travel speeds respectively corresponding a plurality of time periods, the travel speed corresponding to each time period is obtained by averaging speeds of a mobile body on the subject road for each time period; and the speed similarity degree calculating unit calculates the speed similarity degree by comparing, for each time period, the travel speed associated with the subject road and the travel speed of a corresponding time period of each of the plurality of sections. 4. The travel speed estimating device according to claim 1, wherein the total similarity degree calculating unit calculates the total similarity degree based on the speed similarity degree, the environment similarity degree, a weight coefficient applied to the speed similarity degree, and a weight coefficient applied to the environment similarity degree. 5. The travel speed estimating device according to claim 4, wherein the weight coefficient applied to the speed similarity degree and the weight coefficient applied to the environment similarity degree are set to sum to a fixed value. 6. The travel speed estimating device according to claim 4, wherein the weight coefficient applied to the speed similarity degree is set according to a data amount of speed for each mobile body accumulated for each of the plurality of sections. 7. The travel speed estimating device according to claim 1, wherein the estimating unit complements a travel speed on the subject road for a time period unassociated with the travel speed using the travel speed of a corresponding time period of the selected section. 8. The travel speed estimating device according to claim 1, wherein the environment information includes at least one of population of a section including the subject road, road length and number of traffic lights for each road type, and road length and number of traffic lights for each lane. 9. The travel speed estimating device according to claim 1, wherein the holding unit holds the travel speed set for each road type; and the speed similarity degree calculating unit calculates a similarity degree of the travel speed set for a road type of the subject road and, among the travel speeds associated with the plurality of sections, the travel speed corresponding to the road type of the subject road as the speed similarity degree. 10. A method for estimating a travel speed of a mobile body, the method comprising: specifying a subject road, which is subject to travel speed estimation, from roads in map information; dividing a map in the map information into a plurality of sections; calculating a speed similarity degree, which is a similarity degree of a travel speed associated with the subject road and a travel speed associated with each of the plurality of sections; calculating an environment similarity degree, which is a similarity degree of environment information corresponding to one of the plurality of sections including the subject road and environment information corresponding to each of the plurality of sections; calculating a total similarity degree based on the calculated speed similarity degree and environment similarity degree for each section; and estimating the travel speed on the subject road when accumulation of the travel speed associated with the subject road is insufficient to estimate the travel speed on the subject road, wherein the estimating the travel speed includes selecting a section similar to the section including the subject road from the plurality of sections based on the total similarity degree and setting the travel speed associated with the selected section as a travel speed of a corresponding time period on the subject road.