Regulation variable technique

John Graham uses the same regulation variable technique in another related study which covers the period 1947 to 1981. He estimates the reduced form equation for a model in which fatality rate and speed are determined simultaneously. In practical terms, the only new variable is a dummy variable for the 55 m.p.h. speed limit. Curiously the price of gas is ignored despite theory and evidence that it is a determinant of speed. This misspecification may explain the large size (39 percent for 1981) of the estimated reduction in the occupant fatality rate. He finds some weak evidence that nonoccupants are made less safe m that the (insignificant) regulation coeffident in the pedestrian... 

The apparatus consists of a chromatography column and a flow controller (Fig. 2.141). This figure is reproduced from the original literature report, to illustrate the description of the technique below, but the equipment is commercially available (e.g. Aldrich Chemical Co., May and Baker Ltd). The flow controller is a simple variable bleed device for precise regulation of the elution rate and is constructed from a glass/Teflon needle valve. Eluate fractions are collected in... 

The densitometer uses a two beam comparator technique of measurement. A single lamp illuminates, through a variable neutral density filter, the emitter of an eleven stage photomultiplier tube. Because the frequency of measurement is five times the AC line frequency and the amplifiers are extremely high gain, the lamp must be operated from a regulated DC source, otherwise, 120 Hz brightness ripple of the lamp is recorded in the data. 

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