Using the Federal Rules of Evidence. What would be a given analysis of this scenario?

On an open stretch of a two-lane highway in Nevada Jay Gadsby, traveling eastbound in a red Z -car with racing stripes, collided with Roy Reinhart headed westbound in a pickup truck with a gunrack. Both Jay and Roy were killed instantly. The road was straight, the noon-day sun bright overhead, and afternoon thermal winds had not yet picked up - in short driving conditions were optimal. Physical facts yield no clues as to the cause of the accident.

In her wrongful death action against Gabsby's estate, Roy's widow offers testimony by another eastbound driver - one Hill who was the first to come upon the accident - that 30 miles west of the point of collision the red Z car had overtaken him going "at least 80 mph." The defense objects, arguing that Hill's testimony is "irrelevant" when he offered as proof Jay was speeding at the time of the accident, at least in the absence of further proof that Gadsby likely continued to travel at the rate observed for the 30 miles between the sighting and the point of impact.

1. Is the evidence relevant to the question of Gadsby's speed at the time of impact ?

2. Should the judge admit the evidence only if the proponent offers additional proof to satisfy the condition suggested by the defendant ?