22 of the shield 9 is contained within the groove 19 the width of the grooves 17 and 19 is dimensioned to form snug sliding engagements with the shield 9 the ledges 25 of the lens 11 are generally tapered as shown in fig2 such that wind noise arising from the ledges 25 is minimized as the emergency vehicle 15 is driven at high speeds the latching means 7 comprise portions of the lens 11 adjacent to the shield 9 formed into ridges 27 the extremities of which substantially align with an outer face 29 of the shield 9 as shown in fig3 the ridges 27 are spaced apart such that opposing ends 31 of the shield 9 are spaced in close proximity to the ridges 27 as the upper and lower edges 21 and 22 of the shield 9 are retained within the grooves 17 and 19 as shown in fig3 and 4 alternatively the ridges 27 may be eliminated such that the shield 9 can be slidably removed laterally from the grooves 17 and 19 preferably however the shield 9 is displaced minimally laterally in order to avoid damage to the shield 9 and to a portion 33 of the lens 11 underlying the shield 9 from being scratched by debris such as dust or the like disposed between the shield 9 and the lens portion 33 the.