Thermal cameras care about more than just the absolute temperature of an object. The emissive and reflective properties of the material (in infrared) also matter significantly. A human being would almost certainly be visible in a thermal imaging view of that scene.

When you walk outside in the daytime, everything is bathed in a uniform light from the sun, but you have no trouble distinguishing between objects, as they emit and reflect light differently.

> The high today was 92F.

Probably not relevant to conditions at 10pm on Monday, when it was between 70F and 57F (the range for 6pm Monday to 12am Tuesday.)

> Pavement would almost certainly be warmer than that.

Sure, when it was 92F the pavement would probably be 140+F.

> How's a thermal camera supposed to detect 98F on a background that is proably +/- 5 degrees of that?

At night, the pavement would be much cooler than a human; at the high temperature you report, it would probably be much hotter; there's a place in between where the problem you have would be occur, sure, but it's neither at the high nor, more to the point, in the conditions when the accident occurred.

So, if the asphalt is 140F when it's 92F, what's it when it's 65? About 100?

The reason why it's so hot is because of radiated heat from the sun. It'd be much closer to air temp at 10 pm, well after sunset.

See comment above. We routinely walk around (and avoid objects) even though the entire field is uniformly bathed in the light of a single light source.

If you redefine the temperature scale so 90F is 0, then that difference between 98 and 92 becomes the difference between 8 and 2, which suddenly looks a lot more significant. So I think your concern is based more on the arbitrary 0 of the F scale.

If a thermal camera can't detect a person on the road, then a thermal camera is the wrong camera to use. The exact technology isn't important - the important thing is, the vehicle failed to detect a human being crossing in front of it.

That's the temperature at the peak of day, right? The temperature in the middle of the night, when the crash occurred, should be closer to the low.

Even lows are still in the upper 70s, and again, asphalt will absorb heat during the day and then release it at night. 10pm isn't exactly "middle of the night", either, it's only 3 hours after sunset.

Unless you're going downhill, FLIR (forward looking infrared) should not be pointing at asphalt.

There would still be situations when you'd be attempting to detect a human with a hot asphalt background. Such as a crosswalk at the base of a hill (C is the car and X is the crosswalk):

          ______
         /
 C____X_/