A navigation system for a host vehicle, the navigation system comprising: at least one processor programmed to: receive, from a camera (122, 124, 126), a plurality of images representative of an environment of the host vehicle; analyze at least one of the plurality of images to identify navigational state information associated with the host vehicle; determine a plurality of potential trajectories for the host vehicle based on the navigational state information; characterised in that the at least one processor is further programmed to: perform a preliminary analysis relative to each of the plurality of potential trajectories to determine whether each of the plurality of potential trajectories is in compliance with one or more navigational safety constraints; select, based on the preliminary analysis, a subset of the plurality of potential trajectories, wherein the subset of the plurality of potential trajectories includes fewer potential trajectories than the plurality of potential trajectories, wherein the preliminary analysis is based on one or more predetermined safety constraints; perform a secondary analysis relative to the subset of the plurality of potential trajectories, and based on the secondary analysis, select one of the subset of the plurality of potential trajectories as a planned trajectory for the host vehicle, wherein the secondary analysis is based on a policy gradient technique; determine one or more navigational actions for the host vehicle based on the planned trajectory selected from among the subset of the plurality of potential trajectories; and cause at least one adjustment of a navigational actuator of the host vehicle to implement the one or more navigational actions for the host vehicle. receive, from a camera (122, 124, 126), a plurality of images representative of an environment of the host vehicle; analyze at least one of the plurality of images to identify navigational state information associated with the host vehicle; determine a plurality of potential trajectories for the host vehicle based on the navigational state information; characterised in that the at least one processor is further programmed to: perform a preliminary analysis relative to each of the plurality of potential trajectories to determine whether each of the plurality of potential trajectories is in compliance with one or more navigational safety constraints; select, based on the preliminary analysis, a subset of the plurality of potential trajectories, wherein the subset of the plurality of potential trajectories includes fewer potential trajectories than the plurality of potential trajectories, wherein the preliminary analysis is based on one or more predetermined safety constraints; perform a secondary analysis relative to the subset of the plurality of potential trajectories, and based on the secondary analysis, select one of the subset of the plurality of potential trajectories as a planned trajectory for the host vehicle, wherein the secondary analysis is based on a policy gradient technique; determine one or more navigational actions for the host vehicle based on the planned trajectory selected from among the subset of the plurality of potential trajectories; and cause at least one adjustment of a navigational actuator of the host vehicle to implement the one or more navigational actions for the host vehicle. perform a preliminary analysis relative to each of the plurality of potential trajectories to determine whether each of the plurality of potential trajectories is in compliance with one or more navigational safety constraints; select, based on the preliminary analysis, a subset of the plurality of potential trajectories, wherein the subset of the plurality of potential trajectories includes fewer potential trajectories than the plurality of potential trajectories, wherein the preliminary analysis is based on one or more predetermined safety constraints; perform a secondary analysis relative to the subset of the plurality of potential trajectories, and based on the secondary analysis, select one of the subset of the plurality of potential trajectories as a planned trajectory for the host vehicle, wherein the secondary analysis is based on a policy gradient technique; determine one or more navigational actions for the host vehicle based on the planned trajectory selected from among the subset of the plurality of potential trajectories; and cause at least one adjustment of a navigational actuator of the host vehicle to implement the one or more navigational actions for the host vehicle.