Understanding FMVSS 105: Parking Brake Standards

Federal Motor Vehicle Safety Standard (FMVSS) No. 105, titled 'Hydraulic and electric brake systems,' is a crucial regulation that sets the minimum performance benchmarks for a vehicle's service and parking brake systems. Initially, this standard was exclusively applied to passenger cars equipped with hydraulic brake systems. However, over time, the National Highway Traffic Safety Administration (NHTSA) has undertaken several rulemaking actions to expand its scope and refine its requirements, aiming to bolster overall road safety. A significant amendment extended the parking brake requirements to a broader range of vehicles, including multipurpose passenger vehicles (MPVs), buses, and trucks with a Gross Vehicle Weight Rating (GVWR) exceeding 10,000 pounds (approximately 4,536 kilograms), particularly those utilising hydraulic or electric brake systems. This move was driven by a commitment to safety, ensuring that heavier vehicles, beyond school buses, also meet stringent standards for parking brake efficacy.

The Evolution of FMVSS 105: A Focus on Parking Brakes

The journey of FMVSS 105 began with a focus on passenger cars. However, recognising the diverse needs and potential risks associated with different vehicle types, NHTSA has progressively updated the standard. Key milestones include:

• January 16, 1976: The standard's service and parking brake requirements were extended to school buses with hydraulic service brake systems.
• January 2, 1981: A final rule extended FMVSS 105's parking brake requirements to MPVs, trucks, and buses with a GVWR of 10,000 pounds (4,536 kg) or less. Crucially, this rule mandated that parking brakes on these vehicles must hold them stationary for five minutes on a 30 percent grade, in both forward and reverse directions.
• December 21, 1981: Following petitions for reconsideration, the gradient requirement for parking brakes on these vehicles was adjusted from 30 percent to 20 percent.
• September 30, 1997: FMVSS No. 135 was established, initially for passenger cars only. Later, its applicability was extended to MPVs, trucks, and buses with a GVWR of 7,716 pounds (3,500 kg) or less, vehicles previously regulated under FMVSS No. 105.

The Safety Imperative: Extending Requirements to Heavier Vehicles

A pivotal amendment, proposed on October 30, 2002, sought to extend the minimum performance requirements and associated test procedures for parking brake systems to all vehicles with a GVWR exceeding 10,000 pounds (4,536 kg). The rationale behind this proposal was rooted in a clear safety need:

The Safety Need Explained

Parking brakes are a vital operational safety feature. When properly engaged, they are instrumental in preventing 'driverless roll-away' events – scenarios where a vehicle moves unintentionally, potentially leading to collisions, injuries, and fatalities. NHTSA's analysis of its Fatality Analysis Reporting System (FARS) database revealed instances of fatal roll-away events involving large, hydraulically-braked, non-school bus vehicles. Furthermore, data from the General Estimates System (GES) indicated a significant number of crashes and injuries annually resulting from roll-away heavy-duty trucks, although the specific brake type (hydraulic or air) and parking status were not always definitively recorded. These statistics underscore the potential dangers associated with inadequate parking brake performance in heavier vehicles.

The proposed rule aimed to address two key aspects:

1. Standardisation of Engagement Force: By requiring all heavy vehicles to meet the same parking brake performance requirements, including engagement force limits, NHTSA aimed to reduce the likelihood of misapplication. This is particularly relevant for fleet drivers who operate a variety of vehicles, ensuring a more consistent and predictable user experience. The standard specifies an engagement force limit of not more than 150 pounds for a foot-operated system and 125 pounds for a hand-operated system for vehicles with a GVWR greater than 10,000 pounds.
2. Gradient Holding Capability: The requirement for parking brakes to hold a vehicle stationary on a 20 percent grade, in both forward and reverse directions, is designed to prevent roll-away events on most roads in the United States, as the majority of roads have grades less than 20 percent.

NHTSA posited that most heavy vehicles were already manufactured with parking brakes designed to meet these standards. However, formalising the requirement and mandating certification would provide added assurance of compliance and guard against potential performance degradation due to future design changes. The agency specifically referenced Paragraph S5.2 of the standard, which mandates a friction-type parking brake with a solely mechanical means for engagement, and Paragraph S5.2.3, detailing the 20 percent grade holding requirement.

Costs and Benefits: A Minimal Impact?

Industry feedback suggested that parking brake systems for trucks and buses with GVWRs over 10,000 pounds were generally already designed to meet the FMVSS No. 105 requirements for school buses. Consequently, NHTSA estimated the cost of compliance for manufacturers of non-school buses and trucks to be minimal, estimated at less than $10 per vehicle. The cost of conducting the parking brake compliance test was also deemed insignificant compared to the overall FMVSS No. 105 compliance testing, as the necessary test facilities (e.g., 20 percent grade slopes) were widely available and the test procedures were straightforward. While acknowledging that the safety benefits might be marginal for vehicles already compliant, NHTSA anticipated a reduction in collisions, injuries, and fatalities resulting from driverless roll-away events for those vehicles that did not meet the requirements.

Addressing Additional Issues

The rulemaking also addressed other aspects of FMVSS No. 105:

• Inapplicability to Lighter Vehicles: The application section (S3) was to be amended to reflect that the standard's requirements are inapplicable to hydraulically-braked vehicles with a GVWR of 7,716 pounds (3,500 kg) or less, as these are now covered by FMVSS No. 135.
• SAE J972 Reference Update: A petition from Mr. James E. Stocke led to a proposal to update a reference to the Society of Automotive Engineers' (SAE) Recommended Practice J972 concerning moving barrier collision tests. The update involved re-designating a paragraph within the document, while the technical information remained substantively identical.

Public Comments and NHTSA's Response

NHTSA received comments from various stakeholders, including safety advocacy groups and industry associations. Generally, there was support for extending the parking brake requirements to heavier vehicles.

Key Comment Themes:

• Applicability to Trailers: Several manufacturers sought clarification on whether the new requirements applied to trailers. NHTSA confirmed that the intent was to apply the rule only to MPVs, non-school buses, and trucks over 10,000 pounds GVWR, explicitly stating that FMVSS No. 105 has never been intended to apply to trailers or motorcycles. An error in the existing application section's language was noted and corrected in the final rule.
• Engagement Effort Threshold: One commenter expressed disagreement with the engagement force limits for hand and foot-operated parking brakes, suggesting they might be too high for some operators, including those with disabilities. NHTSA responded that systems with lower force requirements might necessitate costly electrical activation, and noted that FMVSS No. 105 already allows for electrically activated parking brakes with no specific force requirements. Aftermarket solutions were also mentioned.
• Retrofitting: A suggestion to extend the rule to retrofitting parking brakes on existing vehicles was considered but declined, as it was outside the scope of the proposed rulemaking and potentially cost-prohibitive.
• Parking Brake Performance and Maintenance: ArvinMeritor raised concerns about potential variations in parking brake performance due to automatic adjustment issues and different actuation systems. NHTSA noted that parking brake adjustment appears straightforward and inexpensive, and that in-service maintenance is the responsibility of operators, with the Federal Motor Carrier Safety Administration having jurisdiction over such matters for large commercial vehicles.
• Emergency Brake Function: ArvinMeritor also commented that proposed parking brake systems are not designed for emergency braking. NHTSA clarified that the standard does not require parking brakes to provide an emergency brake function, defining an emergency brake as a system to stop a vehicle after a service brake failure.
• Lead Time: The Truck Manufacturers Association suggested a one-year lead time for the new requirements, which NHTSA agreed was adequate. The final rule's effective date was set one year from its publication.

The Final Rule: Mandating Enhanced Parking Brake Safety

In conclusion, NHTSA issued a final rule amending FMVSS No. 105. This amendment officially extends the minimum performance requirements and associated test procedures for parking brake systems to all MPVs, buses, and trucks with GVWRs exceeding 10,000 pounds. The rule clarifies the applicability section (S3) to explicitly state its coverage for these vehicle types with hydraulic or electric brake systems. Furthermore, the reference to SAE J972 was updated, and corrections were made to the title of FMVSS No. 135 and the description of brake warning indicator functions.

Key Requirements Summary for Vehicles > 10,000 lbs GVWR:

The rule's statutory basis is firmly rooted in NHTSA's authority under 49 U.S.C. Chapter 301, ensuring that motor vehicle safety standards are practicable, meet safety needs, and are stated objectively. The agency adhered to informal rulemaking procedures, including public notice and comment, to ensure the final rule reflects comprehensive consideration of relevant safety information and public input.

Regulatory Impact and Compliance

NHTSA conducted analyses concerning Executive Order 12866, the Regulatory Flexibility Act, and the National Environmental Policy Act. The agency determined that the rule would not have significant economic effects. The estimated cost of compliance, less than $10 per vehicle, on an estimated 212,000 vehicles annually, results in a total annual effect well below the threshold for significant economic impact. Consequently, a full regulatory evaluation or Unfunded Mandates assessment was deemed unnecessary. The agency certified that the rule would not have a significant economic impact on a substantial number of small entities.

Frequently Asked Questions:

What is the primary goal of FMVSS No. 105 regarding parking brakes?

The primary goal is to ensure minimum performance requirements for parking brake systems to prevent unintended vehicle movement and enhance road safety.

Which vehicles are covered by the extended parking brake requirements in FMVSS No. 105?

Multipurpose passenger vehicles (MPVs), buses, and trucks with a Gross Vehicle Weight Rating (GVWR) greater than 10,000 pounds (4,536 kg) that are equipped with hydraulic or electric brake systems.

What are the specific performance requirements for parking brakes on these heavier vehicles?

They must be capable of being engaged with a force not exceeding 150 pounds for foot-operated systems and 125 pounds for hand-operated systems, and must hold the vehicle stationary for five minutes on a 20 percent grade in both forward and reverse directions.

Does FMVSS No. 105 apply to trailers?

No, NHTSA has explicitly stated that FMVSS No. 105 has never been intended to apply to trailers or motorcycles.

Are parking brakes required to function as emergency brakes under FMVSS No. 105?

No, the standard does not require parking brakes to provide an emergency brake function.

By standardising and strengthening parking brake requirements for a wider range of heavy vehicles, NHTSA aims to significantly contribute to preventing dangerous roll-away incidents, ultimately making our roads safer for everyone.