Federal Highway Administration, DOT § 393.41
terminals which conform to the SAE tems (except the service brake actu- Standard 1 for ‘‘Cable Terminals’’ or by ation pedal or valve)— cable terminals which are mechani- (i) The vehicle will have operative cally and electrically at least equal to brakes; and such terminals. The number of wires (ii) In the case of a vehicle manufac- attached to any post shall be limited to tured on or after July 1, 1973, the vehi- the number which such post was de- cle will have operative brakes capable signed to accommodate. The presence of performing as specified in § 393.52(b). of bare, loose, dangling, chafing, or (2) A motor vehicle to which the poorly connected wires is prohibited. emergency brake system requirements of Federal Motor Vehicle Safety Stand- Subpart C—Brakes ard No. 105 (§ 571.105 of this title) ap- plied at the time of its manufacture § 393.40 Required brake systems. conforms to the requirements of para- (a) General. A bus, truck, truck trac- graph (c)(1) of this section if— tor, or a combination of motor vehicles (i) It is maintained in conformity must have brakes adequate to control with the emergency brake require- the movement of, and to stop and hold, ments of Standard No. 105 in effect on the vehicle or combination of vehicles. the date of its manufacture; and (b) Specific systems required. (1) A bus, (ii) It is capable of performing as truck, truck tractor, or combination of specified in § 393.52(b), except upon motor vehicles must have— structural failure of its brake master (i) A service brake system that con- cylinder body or effectiveness indicator forms to the requirements of § 393.52; body. and (3) A bus conforms to the require- (ii) A parking brake system that con- ments of paragraph (c)(1) of this sec- forms to the requirements of § 393.41. tion if it meets the requirements of (2) A bus, truck, truck tractor, or a § 393.44 and is capable of performing as combination of motor vehicles manu- specified in § 393.52(b). factured on or after July 1, 1973, must [36 FR 20297, Oct. 20, 1971, as amended at 37 have an emergency brake system that FR 5251, Mar. 11, 1972] conforms to the requirements of § 393.52(b) and consists of either— § 393.41 Parking brake system. (i) Emergency features of the service (a) Every commercial motor vehicle brake system; or manufactured on and after March 7, (ii) A system separate from the serv- 1990, except an agricultural commodity ice brake system. trailer, converter dolly, heavy hauler A control by which the driver applies or pulpwood trailer, shall at all times the emergency brake system must be be equipped with a parking brake sys- located so that the driver can readily tem adequate to hold the vehicle or operate it when he/she is properly re- combination under any condition of strained by any seat belt assembly pro- loading as required by FMVSS 571.121. vided for his/her use. The control for An agricultural commodity trailer, applying the emergency brake system heavy hauler or pulpwood trailer shall may be combined with either the con- carry sufficient chocking blocks to pre- trol for applying the service brake sys- vent movement when parked. tem or the control for applying the (b) The parking brake system shall at parking brake system. However, all all times be capable of being applied in three controls may not be combined. conformance with the requirements of (c) Interconnected systems. (1) If the paragraph (a) of the section by either brake systems specified in paragraph the driver’s muscular effort, or by (b) of this section are interconnected in spring action, or by other energy, pro- any way, they must be designed, con- vided, that if such other energy is de- structed, and maintained so that, upon pended on for application of the park- the failure of any part of the operating ing brake, then an accumulation of mechanism of one or more of the sys- such energy shall be isolated from any common source and used exclusively 1 See footnote 1 to § 393.24(c). for the operation of the parking brake.
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(c) The parking brake system shall be rofitted to meet the requirements of held in the applied position by energy this section within one year from Feb- other than fluid pressure, air pressure, ruary 26, 1987, if the brake components or electric energy. The parking brake have been removed. system shall be such that it cannot be (2) Any motor vehicle being towed in released unless adequate energy is a driveaway-towaway operation must available upon release of the parking have operative brakes as may be nec- brake to make immediate further ap- essary to ensure compliance with the plication with the required effective- performance requirements of § 393.52. ness. This paragraph is not applicable to any [34 FR 15418, Oct. 3, 1969, as amended at 53 FR motor vehicle towed by means of a 49398, Dec. 7, 1988] tow-bar when any other vehicle is full- mounted on such towed motor vehicle § 393.42 Brakes required on all wheels. or any combination of motor vehicles (a) Every commercial motor vehicle utilizing three or more saddle-mounts. shall be equipped with brakes acting on (See § 393.71(a)(3).) all wheels. (3) Any full trailer, any semitrailer, (b) Exception. (1) Trucks or truck tractors having three or more axles— or any pole trailer having a GVWR of (i) Need not have brakes on the front 3,000 pounds or less must be equipped wheels if the vehicle was manufactured with brakes if the weight of the towed before July 25, 1980; or vehicle resting on the towing vehicle (ii) Manufactured between July 24, exceeds 40 percent of the GVWR of the 1980, and October 27, 1986, must be ret- towing vehicle.
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[52 FR 2803, Jan. 27, 1987, as amended at 53 FR 49398, Dec. 7, 1988; 54 FR 48617, Nov. 24, 1989; 59 FR 25574, May 17, 1994; 61 FR 1843, Jan. 24, 1996]
§ 393.43 Breakaway and emergency per square inch nor higher than 45 braking. pounds per square inch. The other means shall be a manually controlled (a) Every motor vehicle, if used to device readily operable by a person tow a trailer equipped with brakes, seated in the driving seat. Its emer- shall be equipped with means for pro- gency position or method of operation viding that in case of breakaway of shall be clearly indicated. In no in- such trailer the service brakes on the stance may the manual means be so ar- towing vehicle will be sufficiently op- ranged as to permit its use to prevent erative to stop the towing vehicle. operation of the automatic means. The (b) Every truck or truck tractor automatic and manual means required equipped with air brakes, when used for by this section may be, but are not re- towing other vehicles equipped with air quired to be, separate. brakes, shall be equipped with two (c) Every truck tractor and truck means of activating the emergency fea- when used for towing other vehicles tures of the trailer brakes. One of these equipped with vacuum brakes, shall means shall operate automatically in have, in addition to the single control the event of reduction of the towing ve- required by § 393.49 to operate all hicle air supply to a fixed pressure brakes of the combination, a second which shall not be lower than 20 pounds manual control device which can be
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used to operate the brakes on the and continued functioning of the tub- towed vehicles in emergencies. Such ing or hose; second control shall be independent of (2) Be installed in a manner that in- brake air, hydraulic, and other pres- sures proper continued functioning of sure, and independent of other con- the tubing or hose; trols, unless the braking system be so (3) Be long and flexible enough to ac- arranged that failure of the pressure on commodate without damage all normal which the second control depends will motions of the parts to which it is at- cause the towed vehicle brakes to be tached; applied automatically. The second con- (4) Be suitably secured against chaf- trol is not required by this rule to pro- ing, kinking, or other mechanical dam- vide modulated or graduated braking. age; (d) Every trailer required to be (5) Be installed in a manner that pre- equipped with brakes shall be equipped vents it from contacting the vehicle’s with brakes of such character as to be exhaust system or any other source of applied automatically and promptly high temperatures; and upon breakaway from the towing vehi- (6) Conform to the applicable require- cle, and means shall be provided to ments of paragraph (b) or (c) of this maintain application of the brakes on section. In addition, all hose installed the trailer in such case for at least 15 on and after January 1, 1981, must con- minutes. form to those applicable subsections of (e) Air brake systems installed on FMVSS 106 (49 CFR 571.106). towed vehicles shall be so designed, by (b) Special requirements for metallic the use of ‘‘no-bleed-back’’ relay emer- brake tubing, nonmetallic brake tubing, gency valves or equivalent devices, coiled nonmetallic brake tubing and brake that the supply reservoir used to pro- hose. (1) Metallic brake tubing, non- vide air for brakes shall be safeguarded metallic brake tubing, coiled non- against backflow of air to the towing metallic brake tubing, and brake hose vehicle upon reduction of the towing installed on a commercial motor vehi- vehicle air pressure. cle on and after March 7, 1989, must (f) The requirements of paragraphs meet or exceed one of the following (b), (c), and (d) of this section shall not specifications set forth in the SAE be applicable to motor vehicles in Handbook, 1985 edition: driveaway-towaway operations. (i) Metallic Air Brake Tubing—SAE § 393.44 Front brake lines, protection. Recommended Practice J1149—Metallic Air Brake System Tubing and Pipe— On every bus, if equipped with air July 76. brakes, the braking system shall be so (ii) Nonmetallic Air Brake Tubing— constructed that in the event any SAE Recommended Practice J844— brake line to any of the front wheels is Nonmetallic Air Brake System Type broken, the driver can apply the brakes B—OCT 80. on the rear wheels despite such break- (iii) Air Brake Hose—SAE Rec- age. The means used to apply the ommended Practice J1402—Automotive brakes may be located forward of the Air Brake Hose and Hose Assemblies— driver’s seat as long as it can be oper- JUN 85. ated manually by the driver when the (iv) Hydraulic Brake Hose—SAE Rec- driver is properly restrained by any ommended Practice J1401 Road Vehi- seat belt assembly provided for use. cle-Hydraulic Brake Hose Assemblies Every bus shall meet this requirement for Use with Non-Petroleum Base Hy- or comply with the regulations in ef- draulic Fluid JUN 85. fect at the time of its manufacture. (v) Vacuum Brake Hose—SAE Rec- [53 FR 49400, Dec. 7, 1988] ommended Practice J1403 Vacuum Brake Hose JUN 85. § 393.45 Brake tubing and hose, ade- (2) Except as provided in paragraph quacy. (c) of this section, brake hose and (a) General requirements. Brake tubing brake tubing installed on a motor vehi- and brake hose must— cle before March 7, 1989, must conform (1) Be designed and constructed in a to 49 CFR 393.45 effective October 31, manner that insures proper, adequate, 1983.
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(c) Nonmetallic brake tubing. Coiled able assurance against accidental dis- nonmetallic brake tubing may be used connection; for connections between towed and (d) Have the vacuum brake engine towing vehicles or between the frame manifold connection at least three- of a towed vehicle and the unsprung eighths inch in diameter. subframe of an adjustable axle of that (e) If installed on a vehicle on or vehicle if— after January 1, 1981, meet require- (1) The coiled tubing has a straight ments under applicable subsections of segment (pigtail) at each end that is at FMVSS 106 (49 CFR 571.106). least 2 inches in length and is encased (f) Splices in tubing if installed on a in a spring guard or similar device vehicle after March 7, 1989, must use which prevents the tubing from fittings that meet the requirements of kinking at the fitting at which it is at- SAE Standard J512–OCT 80 Automotive tached to the vehicle; and Tube Fittings or for air brake systems (2) The spring guard or similar device SAE J246—March 81 Spherical and has at least 2 inches of closed coils or Flanged Sleeve (Compression) Tube similar surface at its interface with the Fittings as found in the SAE Handbook 1 fitting and extends at least 1 ⁄2 inches 1985 edition. into the coiled segment of the tubing from its straight segment. [33 FR 19735, Dec. 28, 1968, as amended at 44 (d) Brake tubing and brake hose, uses. FR 25457, May 1, 1979; 53 FR 49400, Dec. 7, Metallic and nonmetallic brake tubing 1988] is intended for use in areas of the brake system where relative movement in the § 393.47 Brake lining. line is not anticipated. Brake hose and The brake lining on every motor ve- coiled nonmetallic brake tubing is in- hicle shall be so constructed and in- tended for use in the brake system stalled as not to be subject to excessive where substantial relative movement fading and grabbing and shall be ade- in the line is anticipated or the hose/ quate in thickness, means of attach- coiled nonmetallic brake tubing is ex- ment, and physical characteristics to posed to potential tension or impact provide for safe and reliable stopping of such as between the frame and axle in the motor vehicle. a conventional type suspension system (axle attached to frame by suspension § 393.48 Brakes to be operative. system). Nonmetallic brake tubing (a) General rule. Except as provided in may be used through an articulation paragraphs (b) and (c) of this section, point provided movement is less than all brakes with which a motor vehicle 4.5 degrees in a vertical plane, and 7.4 is equipped must at all times be capa- degrees in a transverse horizontal ble of operating. plane. (b) Devices to reduce or remove front- (49 U.S.C. 304, 1655; 49 CFR 1.48(b) and 301.60) wheel braking effort. A motor vehicle may be equipped with a device to re- [38 FR 4333, Feb. 13, 1973, as amended at 44 duce the braking effort upon its front FR 25457, May 1, 1979; 45 FR 46424, July 10, 1980; 47 FR 47837, Oct. 28, 1982; 53 FR 49400, wheels or, in the case of a three-axle Dec. 7, 1988] truck or truck tractor manufactured before March 1, 1975, to remove the § 393.46 Brake tubing and hose con- braking effort upon its front wheels, if nections. that device conforms to, and is used in All connections for air, vacuum, or compliance with, the rules in para- hydraulic braking systems shall: graph (b) (1) or (2) of this section. (a) Be adequate in material and con- (1) Manually operated devices. A struction to insure proper continued manually operated device to reduce or functioning; remove the front-wheel braking effort (b) Be designed, constructed, and in- must not be— stalled so as to insure, when properly (i) Installed in a motor vehicle other connected, an attachment free of leaks, than a bus, truck, or truck tractor; or constrictions, or other defects; (ii) Installed in a bus, truck, or truck (c) Have suitable provision in every tractor manufactured after February detachable connection to afford reason- 28, 1975; or
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(iii) Used in the reduced mode except § 393.50 Reservoirs required. when the vehicle is operating under ad- (a) General. Every commercial motor verse conditions such as wet, snowy, or vehicle using air or vacuum for break- icy roads. ing shall be equipped with reserve ca- (2) Automatic devices. An automatic pacity or a reservoir sufficient to en- device to reduce the front-wheel brak- sure a full service brake application ing effort by up to 50 percent of the with the engine stopped without de- normal braking force, regardless of pleting the air pressure or vacuum whether or not antilock system failure below 70 percent of that pressure or de- has occurred on any axle, must not— gree of vacuum indicated by the gauge (i) Be operable by the driver except immediately before the brake applica- upon application of the control that ac- tion is made. For purposes of this sec- tivates the braking system; and tion, a full service brake application is (ii) Be operable when the pressure considered to be made when the service that transmits brake control applica- brake pedal is pushed to the limit of its tion force exceeds— travel. (A) 85 psig on air-mechanical braking (b) Safeguarding of air and vacuum. (1) systems; or Every bus, truck, and truck tractor, (B) 85 percent of the maximum sys- when equipped with air or vacuum res- tem pressure in the case of vehicles ervoirs and regardless of date of manu- utilizing other than compressed air. facture, shall have such reservoirs so (c) Towed vehicle. Paragraph (a) of safeguarded by a check valve or equiv- this section does not apply to— alent device that in the event of failure (1) A disabled vehicle being towed; or or leakage in its connection to the (2) A vehicle being towed in a source of compressed air or vacuum the driveaway-towaway operation which is air or vacuum supply in the reservoir exempt from the general rule of § 393.42 shall not be depleted by the leak or under paragraph (b) of that section. failure. (2) Means shall be provided to estab- (Sec. 204 of the Interstate Commerce Act, as amended (49 U.S.C. 304); sec. 6 of the Depart- lish the check valve to be in working ment of Transportation Act (49 U.S.C. 1655), order. On and after May 1, 1966, means and the delegations of authority by the Sec- other than loosening or disconnection retary of Transportation and the Federal of any connection between the source Highway Administrator at 49 CFR 1.48 and of compressed air or vacuum and the 301.60, respectively) check valve, and necessary tools for op- [39 FR 26907, July 24, 1974, as amended at 41 eration of such means, shall be pro- FR 29130, July 15, 1976; 41 FR 53031, Dec. 3, vided to prove that the check valve is 1976] in working order. The means shall be readily accessible either from the § 393.49 Single valve to operate all front, side, or rear of the vehicle, or brakes. from the driver’s compartment. Every motor vehicle, the date of (i) In air brake systems with one res- manufacture of which is subsequent to ervoir, the means shall be a cock, June 30, 1953, which is equipped with valve, plug, or equivalent device ar- power brakes, shall have the braking ranged to vent a cavity having free system so arranged that one applica- communication with the connection tion valve shall when applied operate between the check valve and the source all the service brakes on the motor ve- of compressed air or vacuum. hicle or combination of motor vehicles. (ii) Where air is delivered by a com- This requirement shall not be con- pressor into one tank or compartment strued to prohibit motor vehicles from (wet tank), and air for braking is taken being equipped with an additional directly from another tank or compart- valve to be used to operate the brakes ment (dry tank) only, with the re- on a trailer or trailers or as provided in quired check valve between the tanks § 393.44. This section shall not be appli- or compartments, a manually operated cable to driveaway-towaway operations drain cock on the first (wet) tank or unless the brakes on such operations compartment will serve as a means are designed to be operated by a single herein required if it conforms to the re- valve. quirements herein.
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(iii) In vacuum systems stopping the audible or visible continuous warning engine will serve as the required to the driver whenever the pressure of means, the system remaining evacu- the compressed air in the braking sys- ated as indicated by the vacuum gauge. tem is below a specified pressure, which must be at least one-half of the [33 FR 19735, Dec. 25, 1968, as amended at 53 FR 49400, Dec. 7, 1988] compressor governor cutout pressure. (2) The vehicle must have a pressure § 393.51 Warning devices and gauges. gauge which indicates to the driver the (a) General. In the manner and to the pressure in pounds per square inch extent specified in paragraphs (b), (c), available for braking. (d), and (e) of this section, a bus, truck, (d) Vacuum brakes. A vehicle (regard- or truck tractor must be equipped with less of the date it was manufactured) a signal that provides a warning to the having service brakes activated by vac- driver when a failure occurs in the ve- uum or a vehicle towing a vehicle hav- hicle’s service brake system. ing service brakes activated by vacuum (b) Hydraulic brakes. A vehicle manu- must be equipped with— factured on or after July 1, 1973, and (1) A device that provides a readily having service brakes activated by hy- audible or visible continuous warning draulic fluid must be equipped with a to the driver whenever the vacuum in warning signal that performs as fol- the vehicle’s supply reservoir is less lows: than 8 inches of mercury; and (1) If Federal Motor Vehicle Safety (2) A vacuum gauge which indicates Standard No. 105 (§ 571.105 of this title) to the driver the vacuum in inches of was applicable to the vehicle at the mercury available for braking. time it was manufactured, the warning (e) Hydraulic brakes applied or assisted signal must conform to the require- by air or vacuum. A vehicle having a ments of that standard. braking system in which hydraulically (2) If Federal Motor Vehicle Safety activated service brakes are applied or Standard No. 105 (§ 571.105) was not ap- assisted by compressed air or vacuum plicable to the vehicle at the time it must be equipped with both a warning was manufactured, the warning signal signal that conforms to the require- must become operative, before or upon ments of paragraph (b) of this section application of the brakes in the event and a warning device that conforms to of a hydraulic-type complete failure of the requirements of either paragraph a partial system. The signal must be (c) or paragraph (d) of this section. readily audible or visible to the driver. (f) Maintenance. The warning signals, (c) Air brakes. A vehicle (regardless of devices, and gauges required by this the date it was manufactured) having section must be maintained in opera- service brakes activated by compressed tive condition. air (air-mechanical brakes) or a vehicle [37 FR 5251, Mar. 11, 1972, as amended at 53 towing a vehicle having service brakes FR 49400, Dec. 7, 1988] activated by compressed air (air-me- chanical brakes) must be equipped, and § 393.52 Brake performance. perform, as follows: (a) Upon application of its service (1) The vehicle must have a low air brakes, a motor vehicle or combination pressure warning device that conforms of motor vehicles must under any con- to the requirements of either para- dition of loading in which it is found on graph (c)(1) (i) or (ii) of this section. a public highway, be capable of— (i) If Federal Motor Vehicle Safety (1) Developing a braking force at Standard No. 121 (§ 571.121 of this title) least equal to the percentage of its was applicable to the vehicle at the gross weight specified in the table in time it was manufactured, the warning paragraph (d) of this section; device must conform to the require- (2) Decelerating to a stop from 20 ments of that standard. miles per hour at not less than the rate (ii) If Federal Motor Vehicle Safety specified in the table in paragraph (d) Standard No. 121 (§ 571.121) was not ap- of this section; and plicable to the vehicle at the time it (3) Stopping from 20 miles per hour in was manufactured, the vehicle must a distance, measured from the point at have a device that provides a readily which movement of the service brake
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pedal or control begins, that is not fied in the table in paragraph (d) of this greater than the distance specified in section. the table in paragraph (d) of this sec- (c) Conformity to the stopping-dis- tion. tance requirements of paragraphs (a) (b) Upon application of its emergency and (b) of this section shall be deter- brake system and with no other brake mined under the following conditions: system applied, a motor vehicle or (1) Any test must be made with the combination of motor vehicles must, vehicle on a hard surface that is sub- under any condition of loading in stantially level, dry, smooth, and free which it is found on a public highway, of loose material. be capable of stopping from 20 miles (2) The vehicle must be in the center per hour in a distance, measured from of a 12-foot-wide lane when the test be- the point at which movement of the gins and must not deviate from that emergency brake control begins, that lane during the test. is not greater than the distance speci- (d) Vehicle brake performance table:
Service brake systems Emergency brake sys- tems Braking Application force as a Decelera- and braking Application Type of motor vehicle percentage tion in feet distance in and braking of gross ve- per second feet from distance in hicle or per second initial speed feet from combination of 20 m.p.h. initial speed weight of 20 m.p.h.
A. Passenger-carrying vehicles. (1) Vehicles with a seating capacity of 10 persons or less, includ- ing driver, and built on a passenger car chassis ...... 65.2 21 20 54 (2) Vehicles with a seating capacity of more than 10 persons, in- cluding driver, and built on a passenger car chassis; vehicles built on a truck or bus chassis and having a manufacturer's GVWR of 10,000 pounds or less ...... 52.8 17 25 66 (3) All other passenger-carrying vehicles ...... 43.5 14 35 85 B. Property-carrying vehicles. (1) Single unit vehicles having a manufacturer's GVWR of 10,000 pounds or less ...... 52.8 17 25 66 (2) Single unit vehicles having a manufacturer's GVWR of more than 10,000 pounds, except truck tractors. Combinations of a 2-axle towing vehicle and trailer having a GVWR of 3,000 pounds or less. All combinations of 2 or less vehicles in driveaway or towaway operation ...... 43.4 14 35 85 (3) All other property-carrying vehicles and combinations of prop- erty-carrying vehicles ...... 43.5 14 40 90
NOTE: (a) There is a definite mathematical relationship between the figures in columns 2 and 3. If the decelerations set forth in column 3 are divided by 32.2 feet per second per second, the figures in column 2 will be obtained. (For example, 21 divided by 32.2 equals 65.2 percent.) Column 2 is included in the tabulation because certain brake-testing devices utilize this factor. (b) The decelerations specified in column 3 are an indication of the effectiveness of the basic brakes, and as measured in practical brake testing are the maximum decelerations attained at some time during the stop. These decelerations as measured in brake tests cannot be used to compute the values in column 4 because the deceleration is not sustained at the same rate over the entire period of the stop. The deceleration increases from zero to a maximum during a period of brake-system applica- tion and brake-force buildup. Also, other factors may cause the deceleration to decrease after reaching a maximum. The added distance which results because maximum deceleration is not sustained is included in the figures in column 4 but is not indicated by the usual brake-testing devices for checking deceleration. (c) The distances in column 4 and the decelerations in column 3 are not directly related. ``Brake-system application and brak- ing distance in feet'' (column 4) is a definite measure of the overall effectiveness of the braking system, being the distance trav- eled between the point at which the driver starts to move the braking controls and the point at which the vehicle comes to rest. It includes distance traveled while the brakes are being applied and distance traveled while the brakes are retarding the vehicle. (d) The distance traveled during the period of brake-system application and brake-force buildup varies with vehicle type, being negligible for many passenger cars and greatest for combinations of commercial vehicles. This fact accounts for the variation from 20 to 40 feet in the values in column 4 for the various classes of vehicles. (e) The terms ``GVWR'' and ``GVW'' refer to the manufacturer's gross vehicle rating and the actual gross vehicle weight, respectively.
[36 FR 20298, Oct. 20, 1971, as amended at 37 FR 5251, Mar. 11, 1972; 37 FR 11336, June 7, 1972]
§ 393.53 Automatic brake adjusters motor vehicle manufactured on or after and brake adjustment indicators. October 20, 1993, and equipped with a (a) Automatic brake adjusters (hydrau- hydraulic brake system, shall meet the lic brake systems). Each commercial automatic brake adjustment system
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requirements of Federal Motor Vehicle tor, manufactured on or after March 1, Safety Standard No. 105 (49 CFR 571.105, 1998 (except commercial motor vehicles S5.1) applicable to the vehicle at the engaged in driveaway-towaway oper- time it was manufactured. ations), shall be equipped with an (b) Automatic brake adjusters (air brake antilock brake system that meets the systems). Each commercial motor vehi- requirements of FMVSS No. 121 (49 cle manufactured on or after October CFR 571.121, S5.1.6.1(a) for trucks and 20, 1994, and equipped with an air brake buses, S5.2.3 for semitrailers, converter system shall meet the automatic brake dollies and full trailers). adjustment system requirements of (d) ABS malfunction circuits and sig- Federal Motor Vehicle Safety Standard nals for air braked vehicles. (1) Each No. 121 (49 CFR 571.121, S5.1.8) applica- truck tractor manufactured on or after ble to the vehicle at the time it was March 1, 1997, and each single-unit air manufactured. braked vehicle manufactured on or (c) Brake adjustment indicator (air after March 1, 1998, subject to the re- brake systems). On each commercial quirements of paragraph (c) of this sec- motor vehicle manufactured on or after tion, shall be equipped with an elec- October 20, 1994, and equipped with an trical circuit that is capable of signal- air brake system which contains an ex- ing a malfunction that affects the gen- ternal automatic adjustment mecha- eration or transmission of response or nism and an exposed pushrod, the con- control signals to the vehicle’s dition of service brake under-adjust- antilock brake system (49 CFR 571.121, ment shall be displayed by a brake ad- S5.1.6.2(a)). justment indicator conforming to the (2) Each truck tractor manufactured requirements of Federal Motor Vehicle on or after March 1, 2001, and each sin- Safety Standard No. 121 (49 CFR 571.121, gle-unit vehicle that is equipped to tow S5.1.8) applicable to the vehicle at the another air-braked vehicle, subject to time it was manufactured. the requirements of paragraph (c) of [60 FR 46245, Sept. 6, 1995] this section, shall be equipped with an electrical circuit that is capable of § 393.55 Antilock brake systems. transmitting a malfunction signal from (a) Hydraulic brake systems. Each the antilock brake system(s) on the truck and bus manufactured on or after towed vehicle(s) to the trailer ABS March 1, 1999 (except trucks and buses malfunction lamp in the cab of the engaged in driveaway-towaway oper- towing vehicle, and shall have the ations), and equipped with a hydraulic means for connection of the electrical brake system, shall be equipped with circuit to the towed vehicle. The ABS an antilock brake system that meets malfunction circuit and signal shall the requirements of Federal Motor Ve- meet the requirements of FMVSS No. hicle Safety Standard (FMVSS) No. 105 121 (49 CFR 571.121, S5.1.6.2(b)). (49 CFR 571.105, S5.5). (3) Each semitrailer, trailer con- (b) ABS malfunction indicators for hy- verter dolly, and full trailer manufac- draulic braked vehicles. Each hydraulic tured on or after March 1, 2001, and braked vehicle subject to the require- subject to the requirements of para- ments of paragraph (a) of this section graph (c)(2) of this section, shall be shall be equipped with an ABS mal- equipped with an electrical circuit that function indicator system that meets is capable of signaling a malfunction in the requirements of FMVSS No. 105 (49 the trailer’s antilock brake system, CFR 571.105, S5.3). and shall have the means for connec- (c) Air brake systems. (1) Each truck tion of this ABS malfunction circuit to tractor manufactured on or after the towing vehicle. In addition, each March 1, 1997 (except truck tractors en- trailer manufactured on or after March gaged in driveaway-towaway oper- 1, 2001, subject to the requirements of ations), shall be equipped with an paragraph (c)(2) of this section, that is antilock brake system that meets the designed to tow another air-brake requirements of FMVSS No. 121 (49 equipped trailer shall be capable of CFR 571.121, S5.1.6.1(b)). transmitting a malfunction signal from (2) Each air braked commercial the antilock brake system(s) of the motor vehicle other than a truck trac- trailer(s) it tows to the vehicle in front
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of the trailer. The ABS malfunction inches) to any other similarly damaged circuit and signal shall meet the re- area. quirements of FMVSS No. 121 (49 CFR (d) Coloring or tinting of windshields 571.121, S5.2.3.2). and windows. Coloring or tinting of (e) Exterior ABS malfunction indicator windshields and the windows to the im- lamps for trailers. Each trailer (includ- mediate right and left of the driver is ing a trailer converter dolly) manufac- allowed, provided the parallel luminous tured on or after March 1, 1998 and be- transmittance through the colored or fore March 1, 2009, and subject to the tinted glazing is not less than 70 per- requirements of paragraph (c)(2) of this cent of the light at normal incidence in section, shall be equipped with an ABS those portions of the windshield or malfunction indicator lamp which windows which are marked as having a meets the requirements of FMVSS No. parallel luminous transmittance of not 121 (49 CFR 571.121, S5.2.3.3). less than 70 percent. The transmittance restriction does not apply to other win- [63 FR 24465, May 4, 1998] dows on the commercial motor vehicle. (e) Prohibition on obstructions to the Subpart D—Glazing and Window driver’s field of view—(1) Devices mounted Construction at the top of the windshield. Antennas, transponders, and similar devices must § 393.60 Glazing in specified openings. not be mounted more than 152 mm (6 inches) below the upper edge of the (a) Glazing material. Glazing material windshield. These devices must be lo- used in windshields, windows, and cated outside the area swept by the doors on a motor vehicle manufactured windshield wipers, and outside the on or after December 25, 1968, shall at a driver’s sight lines to the road and minimum meet the requirements of highway signs and signals. Federal Motor Vehicle Safety Standard (2) Decals and stickers mounted on the (FMVSS) No. 205 in effect on the date windshield. Commercial Vehicle Safety of manufacture of the motor vehicle. Alliance (CVSA) inspection decals, and The glazing material shall be marked stickers and/or decals required under in accordance with FMVSS No. 205 (49 Federal or State laws may be placed at CFR 571.205, S6). the bottom or sides of the windshield (b) Windshields required. Each bus, provided such decals or stickers do not truck and truck-tractor shall be extend more than 115 mm (41⁄2 inches) equipped with a windshield. Each wind- from the bottom of the windshield and shield or portion of a multi-piece wind- are located outside the area swept by shield shall be mounted using the full the windshield wipers, and outside the periphery of the glazing material. driver’s sight lines to the road and (c) Windshield condition. With the ex- highway signs or signals. ception of the conditions listed in para- [63 FR 1387, Jan. 9, 1998] graphs (c)(1), (c)(2), and (c)(3) of this section, each windshield shall be free of § 393.61 Window construction. discoloration or damage in the area ex- (a) Windows in trucks and truck trac- tending upward from the height of the tors. Every truck and truck tractor, ex- top of the steering wheel (excluding a cept vehicles engaged in armored car 51 mm (2 inch) border at the top of the service, shall have, in addition to the windshield) and extending from a 25 area provided by the windshield, at mm (1 inch) border at each side of the least one window on each side of the windshield or windshield panel. Excep- driver’s compartment, which window tions: shall have sufficient area to contain ei- (1) Coloring or tinting which meets ther an ellipse having a major axis of the requirements of paragraph (d) of 18 inches and a minor axis of 13 inches this section; or an opening containing 200 square (2) Any crack that is not intersected inches formed by a rectangle 13 inches by any other cracks; by 173⁄4 inches with corner arcs of 6- (3) Any damaged area which can be inch maximum radius. The major axis covered by a disc 19 mm (3⁄4 inch) in di- of the ellipse and the long axis of the ameter if not closer than 76 mm (3 rectangle shall not make an angle of
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