A converter dolly is coupled to a trailer by a tow-bar, and the required safety device has to be attached to the towing vehicle. Under 49 CFR 393.70(d)(1), where may it not be attached?

Explanation

49 CFR 393.70(d)(1) prohibits attaching the safety device to the pintle hook, or to any other device on the towing vehicle to which the tow-bar is attached. The point of the rule is independence: a safety device exists to hold the trailer if the tow-bar connection fails, so anchoring it to the very component that could fail would leave both the primary and the backup connection depending on one part. That paragraph carries one narrow exception, for a pintle hook or other device manufactured before July 1, 1973, which may carry the safety device at a place on the pintle hook forging or casting that is independent of the pintle hook itself. The other options reverse or invent the restriction: 393.70(d) actually requires the safety device to be coupled to the frame or an extension of the frame of the towing vehicle, 393.70(d)(8) allows a single safety device to attach on the centerline or within six inches to its right rather than forbidding that zone, and the section sets no forward-of-the-rear-axle prohibition.

Source: 49 CFR 393.70(d)(1)