A network computing system can receive transport requests from user computing devices of requesting users of an on-demand carpool service. The system can further receive sensor data from the user computing devices of each carpool passenger of a vehicle. Based on the sensor data, the system can determine a relative position of each carpool passenger within the vehicle, and based on the relative position of each carpool passenger within the vehicle, the system can transmit route data to a transport provider device of the vehicle to rendezvous with a next carpool passenger at an upcoming pick-up location such that an open seat within the vehicle is adjacent to the next carpool passenger.