The opinion
Concurring Opinion by
Mr. Justice Roberts:
Although I join the Court in its affirmance of the court below, I do so because here the evidence is clear and convincing, establishes a positive identification of the vehicle and its speed, and satisfies the Commonwealth’s burden of proof beyond a reasonable doubt. Nevertheless, the instantaneous electronic timing device employed prompts me to make an additional cautionary observation.
*295 The nature of radar detection and its highway use suggests that evidence which is less clear, definite and certain is not an acceptable basis for conviction; Since the radar, device instantaneously locks in the speed at the precise moment the officer detects that a vehicle is traveling over the speed limit (plus tolerance permitted), basic justice requires that evidence of alleged violation be carefully scrutinized in light of the limited capability of the radar device itself and all, circumstances attending its use.
Prior to the radar provisions, there were two methods of detecting speed violations: (1) by clocking over a one-eighth mile measured stretch and (2) by a tested speedometer measuring the travel over a distance of one-quarter mile. The radar amendment to The Vehicle Code provided the third method to measure speed of a moving vehicle—by an instantaneous detecting device—and permitted conviction upon the results of such measurement. Thus, a motorist whose speed is measured by the first two methods may exceed the speed limit temporarily without fear of arrest and conviction if under the first method he slows his vehicle before traveling the full one-eighth mile, or under the second method he slows his vehicle before traveling the full one-quarter mile. However, under the radar provisions, this temporary or momentary excess speed would not preclude prosecution because the speed of the vehicle is locked in at the instant the vehicle exceeds the speed limit. 1 It is apparent, therefore, that the difference in the methods of measuring speed may deprive a defendant apprehended by radar of the equal protection of the law and may afford an immunity to other *296 operators under the measured stretch requirements which he does not possess.
It would appear that the purpose of the measured stretch requirements, in addition to affording a reasonable basis for calculating speed, is also to allow for a momentary excess due to emergencies, the passing of other vehicles or even for momentary or inadvertent lapses on the part of operators who have no intention of violating the law. Surely, the Legislature did not intend by the radar amendments the unfair result of conferring immunity on a momentary violator in. the one-eighth or one-quarter mile instances to the exclusion of the radar violator whose offense may also be momentary.
The caution is obvious; the radar device must be carefully and fairly used within the sphere of its acknowledged capacity in order to avoid the challenge of lack of uniformity or other improper uses. Only in this way may it be a legally acceptable instrumentality in the search for increased highway safety.
Mr. Chief Justice Bell joins in this opinion.
For example, three motorists, each on a separate highway, and each subjected to one of the three methods of detecting speed, could momentarily all be doing the same excessive rate of speed, but only the motorist detected by radar would be subjected to prosecution.