# US 2009/0271084 A1 · Cruise control system and cruise control method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0271084 A1 - Document ID: US20090271084A1 - Status: Published application - Kind: A1 - Application number: 12/430,569 - Filed: 2009-04-27 - Published: 2009-10-29 - Earliest claimed: 2008-04-28 - Assignees: Toyota Jidosha Kabushiki Kaisha - Inventors: Koji TAGUCHI - Web page: https://patentgrep.com/patent/US20090271084A1 ## CPC - B60W 30/16: Control of distance between vehicles, e.g. keeping a distance to preceding vehicle - B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT ## Abstract A cruise control system includes: a traffic condition acquisition unit that acquires a traffic condition that includes a vehicle density on a road on which a vehicle runs; and a cruise control unit that performs cruise control on the vehicle so that a following distance has a less tendency to decrease as the road gets busier. ## Claims ### Claim 1 A cruise control system comprising: a traffic condition acquisition unit that acquires a traffic condition that includes a vehicle density on a road on which a vehicle runs; and a cruise control unit that performs cruise control on the vehicle so that a following distance has a less tendency to decrease as the vehicle density on the road increases toward a critical density. ### Claim 2 (depends on 1) The cruise control system according to claim 1, wherein the cruise control unit controls the following distance to the vehicle ahead, and increases a feedback gain for determining the following distance as the vehicle density increases toward the critical density. ### Claim 3 (depends on 1) The cruise control system according to claim 1, wherein the cruise control unit performs cruise control such that a target following distance is set so that the vehicle density is smaller than or equal to the critical density. ### Claim 4 (depends on 1) The cruise control system according to claim 1, wherein if the vehicle density is larger than the critical density and the traffic condition is a congested traffic flow, the cruise control unit increases a target following distance as compared with an average following distance in the congested traffic flow. ### Claim 5 (depends on 4) The cruise control system according to claim 4, wherein if the vehicle density is larger than the critical density and the traffic condition is a congested traffic flow, the cruise control unit sets the target following distance so that the vehicle density is smaller than or equal to the critical density. ### Claim 6 (depends on 1) The cruise control system according to claim 1, further comprising: a road information acquisition unit that acquires information of a running section which causes a change in speed of the vehicle on the road, wherein the cruise control unit increases a target following distance in the running section as compared with a target following distance in a section other than the running section. ### Claim 7 (depends on 6) The cruise control system according to claim 6, wherein the cruise control unit sets the target following distance in the running section to a distance such that the vehicle density is smaller than or equal to the critical density. ### Claim 8 (depends on 6) The cruise control system according to claim 6, wherein the road information acquisition unit sets the running section from a point, which is located at a predetermined distance back from a point at which the vehicle decelerates, to the point at which the vehicle decelerates. ### Claim 9 (depends on 8) The cruise control system according to claim 8, wherein the point at which a vehicle decelerates is at least any one of a tunnel, a sag, a tight curve and a merging point. ### Claim 10 (depends on 1) The cruise control system according to claim 1, wherein the traffic condition acquisition unit causes a host vehicle to make a lane change when the host vehicle is running on a road having a plurality of lanes, acquires the vehicle density and a traffic flow rate after the lane change, and calculates the critical density on that road. ### Claim 11 (depends on 1) The cruise control system according to claim 1, wherein the cruise control unit instructs a driver of the vehicle not to decrease a following distance. ### Claim 12 (depends on 1) The cruise control system according to claim 1, wherein the critical density is the vehicle density at which a traffic congestion occurs. ### Claim 13 (depends on 12) The cruise control system according to claim 12, wherein the critical density is the vehicle density at which a traffic flow changes from a free traffic flow to a congested traffic flow, the free traffic flow is a condition in which a traffic flow rate increases with an increase in the vehicle density, and the congested traffic flow is a condition in which the traffic flow rate decreases with an increase in the vehicle density. ### Claim 14 A cruise control method comprising: acquiring a traffic condition that includes a vehicle density on a road on which a vehicle runs; and performing cruise control on the vehicle so that a following distance has a less tendency to decrease as the vehicle density on the road increases toward a critical density. ### Claim 15 (depends on 14) The cruise control method according to claim 14, wherein the cruise control controls a following distance to the vehicle ahead, and increases a feedback gain for determining the following distance as the vehicle density increases toward the critical density. ### Claim 16 (depends on 14) The cruise control method according to claim 14, wherein a target following distance is set so that the vehicle density is smaller than or equal to the critical density. ### Claim 17 A cruise control system comprising: a traffic condition acquisition unit that acquires a traffic condition on a road on which a vehicle runs; and a cruise control unit that performs cruise control on the vehicle so that a following distance has a less tendency to decrease as the road gets busier.