组合车辆测试

Trailers that do not have spring brakes have emergency brakes, which work from the air stored in the trailer air tank. A major leak in the emergency line will cause the tractor protection valve to close and the trailer emergency brakes to come on, but the brakes will hold only if there is air pressure in the trailer air tank. Eventually, the air will leak away and then there will be no brakes. Therefore, it is very important for safety that you use wheel chocks when you park trailers without spring brakes. / 没有弹簧制动的挂车仅靠挂车气罐里的空气维持紧急制动；空气最终会 泄光 ，届时将 没有制动 ，因此必须用 轮挡 。

Brake the same way, regardless of whether you have ABS on the tractor, the trailer, or both. / 无论 ABS 安装在牵引车、挂车，还是两者都有， 制动方法相同 ；ABS 只是帮助防抱死。

If you do cross the air-lines, supply air will be sent to the service line instead of going to charge the trailer air tanks. Air will not be available to release the trailer spring brakes. If the spring brakes don't release when you push the trailer air supply control, check the air-line connections. / 若把两根气管接反，供气会被送到行车管路而非充满挂车储气罐，导致 弹簧制动无法释放 。若按下挂车供气控制后仍不释放，应检查气管连接。

Make sure air pressure is up to normal. / 确保空气压力达到 正常值 。

One good rule says you need at least one second for each 10 feet of vehicle length at speeds below 40 mph. At greater speeds, you must add 1 second for safety. / 一个常用规则： 40 mph 以下 时，每 10 英尺 车长应留 1 秒 间隔；更高速度需 再加 1 秒 。

When a vehicle goes around a corner the rear wheels follow a different path than the front wheels, and this is called off-tracking or "cheating." Longer vehicles will off-track more. If there is more than one trailer, the rear wheels of the last trailer will off-track the most. / 车辆转弯时后轮走出的轨迹与前轮不同，称为“偏轨”。 车越长偏轨越大 ；若有多节挂车，最后一节的偏轨最大。

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 。

Triples have a rearward amplification of 3.5. This means you can roll the last trailer of triples 3.5 times as easily as a five-axle tractor. While the rearward amplification of a double is around 2. / 三挂的 后向放大 约为 3.5，也就是说，它最后一节挂车 比五轴牵引车 更容易翻车约 3.5 倍；双挂约 2。

Use lowest reverse gear. Back tractor slowly under trailer to avoid hitting the kingpin too hard, and stop when the kingpin is locked into the fifth wheel. / 使用 最低倒挡 ，缓慢把牵引车倒到挂车下，避免猛烈撞击牵引销；当牵引销锁入五轮时再停下。

Some vehicles have "dead end" or dummy couplers to which the hoses may be attached when they are not in use. This will prevent water and dirt from getting into the coupler and the air-lines. / 有些车辆配有“死端”假接头，未用时把手爪接头接上去，可防止 水和尘土 进入接头与气管。

The trailer should be low enough that it is raised slightly by the tractor when the tractor is backed under it. Raise or lower the trailer as needed. If the trailer is too low, the tractor may strike and damage the trailer nose; if the trailer is too high, it may not couple correctly. / 挂车应略低于五轮，使牵引车倒入时能将挂车稍微托起。过低可能撞伤挂车鼻部；过高可能无法正确挂接。

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 / 应急管路（亦称 供气管路 ）有两大作用：其一向挂车储气筒供气；其二控制组合车辆的 紧急制动 。

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。

– 45 psi. This will cause the spring brakes to come on. / 反复踩放踏板使气压下降到 20–45 psi ，这会使 弹簧制动介入 。

Shut the engine off so you can hear the brakes. Apply and release trailer brakes and listen for sounds of trailer brakes being applied and released. You should hear the brakes move when applied and air escape when the brakes are released. / 熄火以便听得更清楚；反复施加并释放挂车制动，应能听到作动与泄气的声音。

If there are no dummy couplers, the glad hands can sometimes be locked together. It is very important to keep the air supply clean and free of moisture. / 如果没有“死端”假接头，可把两只手爪接头互锁在一起。关键是保持空气 清洁并无湿气 。

Check that the safety latch is in position over locking lever. On some fifth wheels the catch must be put in place by hand. / 确认 安全卡扣扣在锁柄上方 。某些五轮的卡扣需要手动放置。

There are more things to inspect on a combination vehicle than on a bus or straight truck. First, of course, there is the entire coupling system: the kingpin, the fifth wheel, etc. Next, there is the landing gear of each trailer. Not to mention a few more axels to check. / 组合车要检查的项目 更多 ：不仅有整个挂接系统（牵引销、五轮等），还有各挂车的支腿，以及更多的车轴。

The earliest way to notice that your trailer is jackknifing is to see it swinging out in your mirrors. / 挂车开始形成折刀（jackknife）的最早迹象，是你会从后视镜里看到它向外摆动。

With a fully-charged air system, turn off the engine, release the parking brake; and time the air pressure drop. The loss rate should be less than three psi in one minute for combination vehicles, we do not add the additional second here because the brakes are released. / 气压充满后，熄火、释放驻车制动并计时气压下降；组合车辆在 1 分钟内的压降应 小于 3 PSI 。