A method comprising: obtaining, by a computer system, lane information that provides an estimated location of a lane of a road on which a vehicle is traveling, wherein the computer system is configured to control the vehicle in an autonomous mode; determining, by the computer system, that the lane information has become unavailable or unreliable; and in response to determining that the lane information has become unavailable or unreliable, the computer system: using at least one sensor to monitor at least a first distance and a second distance, wherein the first distance comprises a distance between the vehicle and at least one neighboring vehicle at a first time and the second distance comprises a distance between the vehicle and the at least one neighboring vehicle at a second time, based on the first distance, determining a first relative position of the neighboring vehicle, based on the second distance, determining a second relative position of the neighboring vehicle, based on the first relative position and the second relative position, determining an estimated path of the neighboring vehicle, based on the estimated path, determining an updated estimated location of the lane, and controlling the vehicle based on the updated estimated location of the lane. obtaining, by a computer system, lane information that provides an estimated location of a lane of a road on which a vehicle is traveling, wherein the computer system is configured to control the vehicle in an autonomous mode; determining, by the computer system, that the lane information has become unavailable or unreliable; and in response to determining that the lane information has become unavailable or unreliable, the computer system: using at least one sensor to monitor at least a first distance and a second distance, wherein the first distance comprises a distance between the vehicle and at least one neighboring vehicle at a first time and the second distance comprises a distance between the vehicle and the at least one neighboring vehicle at a second time, based on the first distance, determining a first relative position of the neighboring vehicle, based on the second distance, determining a second relative position of the neighboring vehicle, based on the first relative position and the second relative position, determining an estimated path of the neighboring vehicle, based on the estimated path, determining an updated estimated location of the lane, and controlling the vehicle based on the updated estimated location of the lane. using at least one sensor to monitor at least a first distance and a second distance, wherein the first distance comprises a distance between the vehicle and at least one neighboring vehicle at a first time and the second distance comprises a distance between the vehicle and the at least one neighboring vehicle at a second time, based on the first distance, determining a first relative position of the neighboring vehicle, based on the second distance, determining a second relative position of the neighboring vehicle, based on the first relative position and the second relative position, determining an estimated path of the neighboring vehicle, based on the estimated path, determining an updated estimated location of the lane, and controlling the vehicle based on the updated estimated location of the lane.