组合车辆测试

Wait until the air pressure is normal, then shut engine off so you can hear the brakes. Check brake system for crossed air-lines by: applying and releasing trailer brakes and listen for sound of trailer brakes being applied and released. You should hear the brakes move when applied and air escape when the brakes are released. / 等气压恢复正常后 熄火 以便听清；反复施加并释放挂车制动，应该能听到制动动作与泄气的声音。

Rear wheel braking skids occur when the rear drive wheels lock. Because locked wheels have less traction than rolling wheels, the rear wheels usually slide sideways to "catch up" with the front wheels. With vehicles towing trailers, a drive-wheel skid can let the trailer push the towing vehicle sideways, causing a sudden jackknife. / 当 驱动轮 被锁死时抓地力更差，后轴会横向滑移来“追上”前轮；带挂车时，挂车会 把牵引车侧推 ，形成突然的折刀。

To legally pull a trailer with a GVWR exceeding 10,000 pounds, you'll need a Class A CDL. To pull triples, the doubles / triples endorsement on your CDL is also required. / 牵引 超过 10,000 磅 挂车需要 A 级 CDL ；拖三挂还必须在 CDL 上有 双 / 三挂背书 。

Go under trailer and investigate the back of the fifth wheel. Make sure the fifth wheel jaws have closed around the shank of the kingpin. / 到挂车下方检查五轮，确认锁爪 抱住牵引销的颈部（shank） 。

If the air pressure falls more than the specified psi in one minute for combination vehicles, the air loss rate is too much. Check for air leaks and fix before driving the vehicle. Otherwise, you could lose your brakes while driving. / 组合车辆 1 分钟的允许压降有上限；若超限解释漏气过大。未修好就上路， 可能失去制动 。

Large combination vehicles take longer to stop when they are empty than when they are fully loaded. When lightly loaded, the very stiff suspension springs and strong brakes give poor traction and make it very easy to lock up the wheels. / 大型组合车在空载或轻载时悬架更硬、制动更“猛”，抓地更差，车轮更容易抱死，因此反而更难刹住。

Before inspection the trailer while coupling you need to secure the vehicle. Put transmission in neutral. Put parking brakes on. Shut off engine and take key with you so someone else won't move truck while you are under it. / 检查期间要先 固定车辆 ：变速箱挂 空挡 ，拉驻车制动，熄火并带走钥匙，防止他人移动。

The emergency line, also called the supply line, has two purposes. First, it supplies air to the trailer air tanks. Second, the emergency line controls the emergency brakes on combination vehicles. / 应急（供气）管路有两项作用：向挂车储气筒供气，并控制组合车辆的紧急制动。

Trailers will have yellow ABS malfunction lamps on the left side, either on the front or rear corner. / 挂车 左侧 设有黄色 ABS 故障灯，位置在 前角或后角 。

Once you realize your vehicle is in a skid, you should release the brakes so that the wheels can grip the road again. / 一旦发现车辆进入侧滑，应 松开刹车 ，让车轮重新抓地。

Be very careful about driving bobtail tractors or tractors without semitrailers. Tests have shown that bobtails can be very hard to stop smoothly and can take longer to stop than a tractor-semitrailer loaded to maximum gross weight. / 单跑牵引车（无半挂）不易平顺刹停，测试表明其制动距离可能 长于 满载的牵引车-半挂车。

Make sure surface of parking area can support weight of trailer. / 确保停车区域地面能承受挂车重量。

Glad hands are coupling devices used to connect the service and emergency air-lines from the truck or tractor to the trailer. / glad hands 是用于连接牵引车与挂车 行车 / 应急 空气管路的接头。

Do not use it in driving because of the danger of making the trailer skid. / 行驶中不要用手控阀，以免造成挂车打滑。

Check if fifth wheel is in proper position for coupling: The fifth wheel should be tilted down toward rear of tractor. / 对接前检查五轮姿态：应当 朝向牵引车尾部下倾 。

Make sure air pressure is up to normal before backing under the trailer. / 在把牵引车倒入挂车底下前，确保空气压力达到 正常值 。

Shut off trailer air supply to lock trailer brakes. Ease pressure on fifth wheel locking jaws by backing up gently, applying the parking brake while tractor is pushing against the kingpin. / 关闭挂车供气以锁住挂车制动后， 轻轻向后顶住 牵引销以卸除五轮锁爪压力，同时拉驻车制动。

The tractor protection valve keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak. The tractor protection valve is controlled by the "trailer air supply" control valve in the cab. The control valve allows you to open and shut the tractor protection valve. The tractor protection valve will close automatically if air pressure is low (in the range of 20 to 45 psi). When the tractor protection valve closes, it stops any air from going out of the tractor. / 牵引车保护阀在挂车脱离或发生严重泄漏时保持牵引车 / 卡车制动系统内的气压；当气压过低（通常 20–45 psi）时会自动关闭。测试成功时，驾驶室的“挂车供气”控制会弹出或切到“紧急”位。

Large combination vehicles take longer to stop when they are empty than when they are fully loaded. When empty, the very stiff suspension springs and strong brakes give poor traction and make it very easy to lock up the wheels causing the tractor to jackknife. / 大型组合车在 空载 时比满载更难刹住；悬架更硬、制动更猛，抓地差、更容易抱死并导致折叠。

To test the trailer air brake system, first charge it with air. Push in the red trailer air supply knob or place the tractor protection valve control in the "normal" position. Wait until the air pressure reaches normal before you start your tests. / 测试挂车制动前应先给系统充气——按入红色挂车供气旋钮，或把牵引车保护阀拨到“ 正常 ”位置，待气压正常后再开始测试。