Editing Drag racing (section)

=== Prerace preparations ===
Before each race (commonly known as a pass), each driver is allowed to perform a [[burnout (vehicle)|burnout]], which heats the driving tires and lays rubber down at the beginning of the track, improving traction. The cars run through a "water box" (formerly a "bleach box", before bleach was replaced{{when|date=March 2021}} by flammable traction compound, which produced spectacular, and dangerous, flame burnouts; the hazard led NHRA to mandate use of water in the 1970s<ref name="Drag Illustrated" />).

Modern races are started electronically by a system known as a ''[[Christmas tree (drag racing)|Christmas tree]]'', which consists of a column of lights for each driver/lane, and two light beam sensors per lane on the track at the starting line. Current NHRA trees, for example, feature one blue light (split into halves), then three amber, one green, and one red.<ref>{{cite web |url=http://www.nhra.com/story/2011/4/12/new-tree-implemented-for-visitmyrtlebeachcom-nhra-four-wide-nationals/ |title=Archived copy |access-date=6 May 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110420065503/http://www.nhra.com/story/2011/4/12/new-tree-implemented-for-visitmyrtlebeachcom-nhra-four-wide-nationals/ |archive-date=20 April 2011 }} New Tree implemented for NHRA VisitMyrtleBeach.com Four-Wide Nationals</ref> When the first light beam is broken by a vehicle's front tire(s), the vehicle is "pre-staged" (approximately {{convert|7|in|mm}} from the starting line), and the pre-stage indicator on the tree is lit. When the second light beam is broken, the vehicle is "staged", and the stage indicator on the tree is lit.<ref>[http://www.nhra.com/nhra101/basics.aspx NHRA.com] Basics of Drag Racing</ref> Vehicles may then leave the pre-stage beam, but must remain in the stage beam until the race starts.