第 4 章 · 速度与安全距离
以下是加州 DMV 驾驶手册「速度与安全距离」章节的考试要点整理，中英对照。读完可以直接在上方做这一章的练习题。
基本速度法：安全永远优先于限速数字 The Basic Speed Law: Safety Comes Before the Number
加州「基本速度法」规定，任何时候都不可以开得比当下路况安全的速度更快。这代表就算你没有超过路牌上的限速，只要当时的天气、能见度或车流让那个速度变得不安全，你一样算违法、一样会被开超速罚单。记住一个原则：安全比牌子上的数字更重要，速度要随当下状况调整。
California's Basic Speed Law says you may never drive faster than is safe for the conditions of the moment. This means that even when you are within the posted limit, you can still be ticketed for speeding if rain, poor visibility, or heavy traffic makes that speed unsafe. The guiding idea is simple: safety always outranks the number on the sign, and your speed must adapt to what is actually happening around you.
限速标志怎么读：白底黑字是「理想状况的上限」 Reading Speed Limit Signs: The Ideal-Conditions Maximum
白底黑字的限速标志代表的是「最高」限速，也就是在天气好、路面干、车不多的理想状况下，你最快只能开到的速度，而不是任何情况都可以开到的速度。常见的数字有 25、30、35、40、45、50、55、60、65、70 英里等。遇到下雨、起雾、夜间或堵车时，安全的速度会远低于牌上的数字，必须自己再放慢。
A black-on-white speed limit sign shows the maximum speed, meaning the fastest you may go only under ideal conditions: good weather, dry pavement, and light traffic. It is a ceiling, not a target you are entitled to reach at all times. Common posted values include 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70 mph. In rain, fog, darkness, or congestion, the safe speed drops well below the posted figure, and you are expected to slow down on your own.
25 mph（25 mph）
35 mph（35 mph）
55 mph（55 mph）
65 mph（65 mph）
住宅区与商业区：预设限速 25 英里 Residential and Business Districts: Default 25 mph
在没有另外标示的住宅区或商业区，加州的预设限速是每小时 25 英里。只要看到两旁都是住家、店面或有行人活动，心里就先抓 25。这类区域行人和小孩多，随时可能有人走出来，务必放慢速度、提高警觉。
In residential or business districts with no sign posted otherwise, California's default speed limit is 25 mph. Whenever you see homes, storefronts, or pedestrian activity on both sides, mentally settle on 25 right away. These areas are full of people and children who may step into the roadway at any time, so slow down and stay alert.
学区：有儿童在场时 25 英里，还要格外小心 School Zones: 25 mph When Children Are Present, and Extra Care
在学校附近、有儿童出现又没有其他标示时，距离学校约 500 至 1,000 英尺范围内的限速通常是每小时 25 英里。但要特别注意：光是守住 25 英里并不一定够慢，小孩可能突然冲出，必要时要再进一步减速。小孩子不懂得看车，你必须替他们多留意。
Near a school where children are present and nothing else is posted, the limit within roughly 500 to 1,000 feet of the school is usually 25 mph. Be warned, though: simply holding at 25 is not automatically slow enough, because a child can dart out without warning, and you should reduce speed further when needed. Children do not judge traffic well, so it is your job to watch out for them.
平交道：看不清铁轨两侧 400 英尺时，只能 15 英里 Railroad Crossings: 15 mph When You Cannot See 400 Feet
接近一个没有栅栏、灯号等管制，而且看不清铁轨两侧 400 英尺的平交道时，最高安全限速是每小时 15 英里。放慢到这个速度，你才能随时停下来让火车先行。视线不好就更要慢，千万别拿性命跟火车赌。
When you approach a railroad crossing that has no gates or signals and where you cannot see 400 feet down the tracks in each direction, the maximum safe speed is 15 mph. Slowing to this speed keeps you ready to stop and yield to a train at any moment. When your view is blocked, slow even more, and never gamble your life against a train.
高速公路：最高限速与最低限速 Freeways: Maximum and Minimum Speed Limits
加州大部分高速公路上，一般客车的最高限速是每小时 65 英里，部分路段会标示到 70 英里，一律以路牌为准。高速公路也设有最低限速，因为开得比周围车流慢很多会挡住后车、逼别人急煞或变换车道，反而制造危险，同样可能收到罚单。跟不上车流的速度，就不该上高速公路。
On most California freeways the maximum speed for a regular passenger car is 65 mph, though some stretches are posted up to 70 mph, and you should always follow the sign. Freeways also have minimum speed limits, because driving much slower than surrounding traffic blocks the cars behind you, forces others to brake hard or change lanes, and actually creates danger, which can earn you a ticket too. If you cannot keep up with the flow, you should not be on the freeway.
恶劣天气与路面：雨、雪、冰的减速幅度 Bad Weather and Road Surfaces: How Much to Slow for Rain, Snow, and Ice
路面状况变差时，抓地力也跟着下降，必须主动减速：下雨路面湿滑时，比平常减慢约每小时 5 到 10 英里；压实的积雪路面上，速度大约要降到平常的一半；结冰路面几乎没有抓地力，最高不应超过每小时 5 英里，同时避免急煞和猛打方向盘。越滑就要越慢，宁可慢到像走路。
As the road surface gets worse, traction drops, so you must slow down on purpose. On wet, rainy pavement, cut your speed by about 5 to 10 mph below normal. On packed snow, reduce your speed to roughly half of what you would normally drive. On ice, where there is almost no grip, keep your speed no higher than 5 mph and avoid sudden braking or sharp steering. The slicker it is, the slower you go, even down to walking pace.
跟车距离：三秒原则与需要拉长的情况 Following Distance: The Three-Second Rule and When to Extend It
在良好路况下，跟车至少要保持「三秒」距离：前车经过某个固定点（例如路牌或标线）后，你数三秒才到同一点，这样才有足够的反应时间。如果你跟在摩托车后面、或正在拖曳拖车，因为煞停比较困难，应该把距离拉得比三秒更长，多留一些空间。天气或路况变差时，同样要加长跟车距离。
In good conditions, keep at least a three-second following distance: after the car ahead passes a fixed point such as a sign or lane marking, you should not reach that same point until you have counted three seconds, which gives you enough time to react. If you are behind a motorcycle or towing a trailer, stopping is harder, so stretch the gap to more than three seconds and leave extra room. In poor weather or on bad surfaces, lengthen the gap as well.
眼睛要往前扫视：预留反应时间 Keep Your Eyes Moving: Scanning Ahead to Buy Reaction Time
好的驾驶人视线要持续移动，向前扫视大约 10 到 15 秒车程的路况，而不是只盯着正前方的车尾。往前看得够远，才能及早发现危险、提早调整速度，替自己留下充足的反应时间。眼睛动，车才安全。
A good driver keeps the eyes moving and scans the road about 10 to 15 seconds of travel ahead, instead of staring only at the bumper directly in front. Looking far enough ahead lets you spot hazards early, adjust your speed in advance, and give yourself plenty of time to react. Moving eyes make for a safer drive.
并入与转弯：先把速度调对再动作 Merging and Turning: Get Your Speed Right Before You Act
使用匝道进入高速公路时，要在匝道上先加速到与高速公路车流相近的速度，再顺畅并入，这样才安全又不挡车。准备在路口转弯时，则要在进入转弯「之前」就先减速到安全的转弯速度，转弯当中才能稳稳控制方向，避免打滑或冲出车道。原则是：并入前先加速，转弯前先减速。
When entering a freeway from an on-ramp, use the ramp to accelerate up to a speed close to the freeway traffic, then merge smoothly so you are safe and do not block others. When preparing to turn at an intersection, slow to a safe turning speed before you enter the turn, so you can control your direction steadily through it and avoid skidding or running out of your lane. The rule is: speed up before you merge, and slow down before you turn.