> which I haven't actually read) is also imprecise in mandating technology that doesn't currently exist.

The technology exists.

The law is at https://www.congress.gov/bill/117th-congress/house-bill/3684... .

The definition is:

In this section:
(1) Advanced drunk and impaired driving prevention
technology.--The term ``advanced drunk and impaired driving
prevention technology'' means a system that--
(A) can--
(i) passively monitor the performance of a
driver of a motor vehicle to accurately identify
whether that driver may be impaired; and
(ii) prevent or limit motor vehicle operation
if an impairment is detected;
(B) can--
(i) passively and accurately detect whether
the blood alcohol concentration of a driver of a
motor vehicle is equal to or greater than the
blood alcohol concentration described in section
163(a) of title 23, United States Code; and
(ii) prevent or limit motor vehicle operation
if a blood alcohol concentration above the legal
limit is detected; or
(C) is a combination of systems described in
subparagraphs (A) and (B).

In the findings:

(4) according to the Insurance Institute for Highway Safety,
advanced drunk and impaired driving prevention technology can
prevent more than 9,400 alcohol-impaired driving fatalities
annually; and

That publication is at https://www.iihs.org/news/detail/alcohol-detection-systems-c... .

"""Manufacturers such as Volvo have experimented with offering alcohol-detection systems as optional equipment. A public-private partnership called the Driver Alcohol Detection System for Safety (DADSS) project is also road-testing a passive alcohol sensor that detects the driver’s blood-alcohol content (BAC) by measuring the ambient air in the vehicle. How many lives the technology might save would depend on how it is implemented."""

Driver Alcohol Detection System for Safety lists two technologies, "Breath System" and "Touch System" at https://dadss.org/ with https://dadss.org/news/updates/when-might-the-dadss-technolo... listing timelines showing the technology exists, and should de deployable well within the time limits of the legislation.

> You want a computer to decide on whether the driver is too drunk to drive, but how do you determine that?

See the DADSS link.

See https://www-esv.nhtsa.dot.gov/Proceedings/27/27ESV-000293.pd... for "DRIVER ALCOHOL DETECTION SYSTEM FOR SAFETY (DADSS) – A VEHICLE SAFETY TECHNOLOGY APPROACH TO REDUCING ALCOHOL-IMPAIRED DRIVING – A STATUS UPDATE", which also points to "SAE J3214 standard, Breath-Based Alcohol Detection System, finalized in January 2021, which was specifically developed to provide the testing specifications adopted for breath sensors in fleet vehicles" (available For $114 at https://www.sae.org/standards/content/j3214_202101/ ).

See https://www-esv.nhtsa.dot.gov/Proceedings/27/27ESV-000291.pd... for "DRIVER ALCOHOL DETECTION SYSTEM FOR SAFETY (DADSS) – RISK BASED APPROACH TO ALCOHOL SENSING OUTCOMES MODELING" describing how they balance the issues.

> And what do you do if you decide the driver is too drunk? Killing the car is a terrible idea if this decision is made in busy traffic at speed. Should an autopilot take over?

The legislation says only "prevent or limit motor vehicle operation if an impairment is detected". It directs the National Highway Traffic Safety Administration to figure out the details. It could be that preventing the car from starting is determined to be the only requirement.

> This shouldn't be hidden away in another giant bill

This looks very much like what goes into giant bills. DADSS has been in development for over a decade.

Nothing seems wrong with the law.