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Federal Motor Vehicle Safety Standards; Review: Antilock Brake Systems, Heavy Trucks; Evaluation Plan; Review: Rear Impact Guards, Truck Trailers; Evaluation Plan

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Information about this document as published in the Federal Register.

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National Highway Traffic Safety Administration (NHTSA), Department of Transportation.


Notice of evaluation plan.


This notice announces NHTSA's publication of a plan for reviewing and evaluating its existing Safety Standards 121, Air Brake Systems, 223, Rear Impact Guards, and 224, Rear Impact Protection. The plan's title is Proposed Evaluations of Antilock Brake Systems for Heavy Trucks and Rear Impact Guards for Truck Trailers. The plan is available on the Internet for viewing on line at​cars/​rules/​regrev/​evaluate/​121223.html.

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Charles J. Kahane, Chief, Evaluation Division, NPP-22, Plans and Policy, National Highway Traffic Safety Administration, Room 5208, 400 Seventh Street, SW, Washington, DC 20590. Telephone: 202-366-2560. FAX: 202-366-2559. E-mail:

John L. Jacobus, Mechanical Engineer, NPP-21, Plans and Policy, National Highway Traffic Safety Administration, Room 5208, 400 Seventh Street, SW, Washington, DC 20590. Telephone: 202-366-2586. FAX: 202-366-2559. E-mail:

For information about NHTSA's evaluations of the effectiveness of existing regulations and programs: Visit the NHTSA web site at and click “Regulations & Standards” underneath “Car Safety” on the home page; then click “Regulatory Evaluation” on the “Regulations & Standards” page.

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As required by the Government Performance and Results Act of 1993 and Executive Order 12866 (58 FR 51735), NHTSA reviews existing regulations to determine if they are achieving policy goals. Safety Standard 121 (49 CFR 571.121) requires Antilock Brake Systems (ABS) on air-brake equipped truck-tractors manufactured on or after March 1, 1997 and on semi-trailers and single-unit trucks equipped with air brakes and manufactured on or after March 1, 1998. Safety Standards 223 (49 CFR 571.223) and 224 (49 CFR 571.224) set minimum requirements for the geometry, configuration, strength and energy absorption capability of rear impact guards on full trailers and semi-trailers over 10,000 pounds Gross Vehicle Weight Rating manufactured on or after January 26, 1998. NHTSA's Office of Plans and Policy is planning to obtain crash data and statistically evaluate the effectiveness of ABS and rear impact guards for heavy trucks.

NHTSA proposes to work with the State police from at least two large States. They will send data to NHTSA on every crash they investigate that involves a tractor-trailer, a bobtail tractor, or a medium or heavy single-unit truck. The data will include the basic State crash report plus a supplemental form identifying if the truck or trailer are ABS-equipped (as evidenced by presence of the malfunction indicator lights). The data will comprise approximately 10,000 tractor-trailer crashes and 5,000 single-unit trucks. On the subset of approximately 1,000 truck-trailers and 700 single-unit trucks that were hit in the rear by the front of a passenger vehicle, police will fill out a second supplemental form describing the rear impact guard on the trailer and the damage pattern on the passenger vehicle. Data collection will start in January 2001, or as soon as feasible after that, and run for two years. NHTSA believes these samples will be adequate for statistically evaluating ABS and rear impact guards.

The purpose of ABS is to help maintain directional stability and control during braking, and possibly reduce stopping distances on some road surfaces, especially on wet roads. ABS could reduce crashes involving jackknife, loss-of-control, run-off-road, lane departure, or skidding, or where trucks with conventional brakes were unable to stop in time to avoid hitting something frontally. On the other hand, ABS is unlikely to affect a control group of crashes where the truck was standing still, moving too slowly for ABS activation, or proceeding straight ahead when another vehicle unexpectedly hit it in the side or rear. The ratios of the various crash types where ABS has potential benefits to control group crashes will be compared for tractor-trailers where both units are equipped with ABS versus tractor-trailers where neither unit is equipped; also for ABS-equipped single-unit trucks vs. non-equipped trucks.

The goal of a rear impact guard is to arrest the forward motion of the striking passenger vehicle and prevent a damage pattern called “underride with passenger compartment intrusion (PCI)” that is dangerous for occupants of the passenger vehicle. The proportion of rear impacts that result in underride with PCI will be compared for trailers with guards that meet NHTSA and/or industry standards versus older trailers with guards that do not meet NHTSA or industry standards. Since the NHTSA standard does not apply to single-unit trucks, the analysis for these trucks will be limited to estimating the overall incidence rate of underride with PCI in rear-impact crashes.

The full text of the plan is available on the Internet for viewing on line at​cars/​rules/​regrev/​evaluate/​121223.html.

How Can I Influence NHTSA's Thinking on This Evaluation?

NHTSA welcomes your review and suggestions on the evaluation plan. You may send your suggestions or comments to Mr. Kahane or Mr. Jacobus, by e-mail, phone or letter, at the addresses shown above, preferably by October 1, 2000.

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Authority: 49 U.S.C. 30111, 30168; delegation of authority at 49 CFR 1.50 and 501.8.

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William H. Walsh,

Associate Administrator for Plans and Policy.

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[FR Doc. 00-20493 Filed 8-11-00; 8:45 am]