the window openings in the of a vehicle US DOT Term: For openings on the side of the vehicle, other than a door opening, the locus of all points where a horizontal line, perpendicular to the vehicle longitudinal centerline, is tangent to the periphery of the opening. US DOT Term: For openings on the front and rear of the vehicle, other than a door opening, daylight opening means the locus of all points where a horizontal line, parallel to the vehicle longitudinal centerline is tangent to the periphery of the opening. Daytime Running Lamp (DRL) A daytime running lamp (DRL, also daytime running light) is an automotive lighting and bicycle lighting device on the front of a roadgoing motor vehicle or bicycle,[1] automatically switched on when the vehicle is in drive, emitting white, yellow, or amber light. Their job isn't to help the driver see the road but to help other road users see the vehicle. Dash-to-Axle (ratio) The critical relationship between front wheel centers and the windshield base. The most notable differences can be seen between cars with front-engine, front-wheel drive layout and front mid-engine, rear-wheel drive layout: the former tend to have longer front overhangs with a smaller dash-to-axle ratios, while the latter have shorter front overhangs with much greater dash-to-axle. Most so called premium vehicles (equipped with rear wheel drive) feature a relatively long dash-to-axle ratio. Deck The horizontal surface at the rear of the car, which usually serves as the trunk lid. Dog leg The area behind the rear door on a four-door car. This area is part of the quarter panel just behind the door and in front of the rear wheel house. Down the Road Graphics (DRG) The styling of the front end of the car, which people will instantly recognize and associate with a manufacturer. For example, the grille, lights and sometimes the DLO. Droptop A convertible. F Fairing An external structure added to increase streamlining, deflect wind, and reduce drag. Fascia The body-skin panel at the front of the car. Fastback A car body style whose roofline slopes continuously down at the back found on cars with a single convex curve from the top to the rear bumper. Fender (wings, UK) Term for cowl covering the wheels of the vehicles. In more modern automobiles, this refers generally to the body panel or panels starting at the front "bumper" to the first door