Revealing mistake: Squad 51 has a flashing light-bar mounted on the roof of the vehicle. There is about 4-5" of space between the length of the light frame and the roof, which means that Squad 51's surrounding environment is easily visible through that gap in normal shots. The hiccup here are certain close-ups of Gage and DeSoto while they're 'driving', because that gap is covered (with red to match the vehicle) and sometimes, when it's daylight, the gap is dark. The same thing happens with the space behind the cab unit (seen through the window), with the red blocking the opening.
Revealing mistake: When Engine 51 and/or Squad 51 are dispatched, the shots of the vehicles when they are first dispatched, while en route to the call or en route to Rampart, etc, in many instances, are stock footage or repeat shots which show the same traffic, same parked cars, same people, etc., from previous episodes.
Revealing mistake: When Squad 51 is dispatched from the stationhouse, the exterior shots show buildings, traffic, trees, etc., they pass along the way. In some close-up shots of Gage and DeSoto while en route, too much of the vehicle's left and/or right sides are visible, which actually shows nothing but a blank screen behind them.
Revealing mistake: In many of Dixie's close-ups the use of the soft focus lens is rather apparent. This could be an acceptable directorial decision, were it not for the fact that in some shots where there's movement (of a hand, for example) that passes through the corners of the shot, the thick 'hazy cloud' is blatantly visible and quite distracting.
Answer: It is standard practice to wet down driveways so that they stand out in a long shot.
stiiggy