Ethics
Any ideas on the ethical implication of the doppler speed radar gun?

 

Yes. What are your concerns, if any?

 

Yes. What are your concerns, if any?

Safety of using speed readers on road. Any dangers of using the reader guns?

 

No biological damage has been shown in humans exposed to such gun radiation at a distance.

 

Any dangers of using the reader guns?

Only to your bank account if you were speeding.

 

The frequencies used by them are 18-40 GHz, depending on the type (they used to be lower frequency, but they were more-easily detectable), placing them solidly in the upper ranges of radio frequencies. So, the corresponding wavelengths are about 7.5-16.7 mm long. These wavelengths are quite long, compared to any biological systems of concern.

Furthermore, the energy carried in the beam (~0.000166 eV) is extremely low - not enough to ionize even a single hydrogen atom (requires 13eV), much less a complicated molecule like DNA or the lipid membranes of your cells (in other words, it cannot cause cellular/genetic damage or free radicals).

The frequencies used are also not at resonance (rotational or translational) frequencies of water, so they won't cause any heating either. Generally, only the UV spectrum (starting at ~800THz and wavelengths <380nm, with energies of >10eV) and higher (like X-rays and gamma rays) are considered "dangerous" - not the visible light spectrum and lower (like IR, UHF, or radio frequencies). There's even an alternative to X-ray imaging called "Terahertz imaging" which is starting to gain some traction in research areas because it is non-ionizing and, overall, much safer.

So, that's why there's no ethics concern: these wavelengths physically cannot harm drivers - not even ones with pacemakers (for perspective, due to Wi-Fi, radio, and cellular service frequencies, we're constantly surrounded by comparable frequencies). And, as @shortbus put it, the only danger it poses is to your bank account (and driving record).

 

Any dangers of using the reader guns?

There is to the officer using it if (s)he steps into the road to take a measurement.

 

I find speed traps set up on a sunny day 200 m before speed change sign to be morally unethical. I find lack of police on the road when conditions are undrivable even more so...

 

Safety of using speed readers on road. Any dangers of using the reader guns?

I don't think I'd want one aimed at me close up because microwave energy can cook you.

 

FCC FAQ on RF Safety.

 

I don't think I'd want one aimed at me close up because microwave energy can cook you.

Microwave energy at specific frequencies and sufficiently-high power can cook you. While water has some rotational modes all throughout the X- and K-bands of the electromagnetic spectrum, radar guns are restricted by FCC regulations on power levels. Modern common/standard LIDAR-based radar guns operate with ~30ns pulses at <50mW power (905 nm wavelength, or 331 THz). By comparison, a microwave oven, which operates at about 2.45 GHz, typically outputs >600W of microwave power (with leakage of <5mW). So, to cook you with a radar gun, it'd take 12000 times longer than a microwave oven takes to heat water, assuming you don't radiate off the energy you absorb faster (depends on how well our bodies retain heat).

As an example, assuming perfect power absorption and continuous-beam LIDAR rather than 30ns pulses, and taking the "cook you" temperature to be roughly 63 C (26 degrees warmer than body temperature), and using my weight in kg (95 kg) and assuming roughly 70% of me is water, it'd take 7.23 MJ of energy to cook me (1729 food calories [kilocalories], for perspective). The standard LIDAR gun would take roughly 4.6 years pointed continuously at me to achieve this. By comparison, a microwave oven would take 3.3 hours to achieve the same thing, if not less.

Would I still want to stand in front of a radar speed gun? Probably not.