A vehicle light bar comprising: a housing sized to extend across and mount to a roof of the vehicle, the housing having two or more lenses which are are for transmitting light from an interior of the housing, and the housing containing at least one circuit board having a planar surface for supporting circuit components extending away from the two or more lenses; the circuit board having patterns of keys (63a, 63b, 63c) in its surface that complements patterns of keys in two or more light beam assemblies so as to register the fastening of the two or more light beam assemblies to the circuit board at predetermined positions; the patterns of keys (63a, 63b, 63c) in the circuit board are associated with electrical connections leading to two or more connectors (87, 115) on the circuit board so as to provide electrical connections between the two or more connectors (87, 115) and the two or more light beam assemblies mated to the circuit board at the predetermined positions defined by the patterns; and characterized in that: - the two or more lenses are distinct from the surrounding area of the housing, - the housing is including components of fasteners (121a, 121b, 121c) complementing components (119a, 119b, 119c) of fasteners in the circuit board such that engagement of the complementing components (119, 121) registers the circuit board to the housing so that the two or more light beam assemblies fastened to the circuit board are automatically aligned with two or more lenses in the housing. a housing sized to extend across and mount to a roof of the vehicle, the housing having two or more lenses which are are for transmitting light from an interior of the housing, and the housing containing at least one circuit board having a planar surface for supporting circuit components extending away from the two or more lenses; the circuit board having patterns of keys (63a, 63b, 63c) in its surface that complements patterns of keys in two or more light beam assemblies so as to register the fastening of the two or more light beam assemblies to the circuit board at predetermined positions; the patterns of keys (63a, 63b, 63c) in the circuit board are associated with electrical connections leading to two or more connectors (87, 115) on the circuit board so as to provide electrical connections between the two or more connectors (87, 115) and the two or more light beam assemblies mated to the circuit board at the predetermined positions defined by the patterns; and characterized in that: - the two or more lenses are distinct from the surrounding area of the housing, - the housing is including components of fasteners (121a, 121b, 121c) complementing components (119a, 119b, 119c) of fasteners in the circuit board such that engagement of the complementing components (119, 121) registers the circuit board to the housing so that the two or more light beam assemblies fastened to the circuit board are automatically aligned with two or more lenses in the housing. - the two or more lenses are distinct from the surrounding area of the housing, - the housing is including components of fasteners (121a, 121b, 121c) complementing components (119a, 119b, 119c) of fasteners in the circuit board such that engagement of the complementing components (119, 121) registers the circuit board to the housing so that the two or more light beam assemblies fastened to the circuit board are automatically aligned with two or more lenses in the housing.