Controlling speed

Key points

1. The best way not to speed is to check your speedometer often.

   Source: Handbook p. 29

   “The best way not to speed is to know how fast you are going. Check the speedometer often.”
   South Dakota Driver License Manual, Handbook p. 29

2. Follow the speed limit signs; they are there for safety.

   Source: Handbook p. 29

   “Follow the speed limit signs. They are there for safety.”
   South Dakota Driver License Manual, Handbook p. 29

3. Drive the maximum limit only in ideal conditions, and reduce speed when conditions require it.

   Source: Handbook p. 35

   “The maximum limit should be driven only in ideal driving conditions, and you must reduce your speed when conditions require it.”
   South Dakota Driver License Manual, Handbook p. 35

4. Driving much slower than traffic is dangerous, and you can be ticketed for impeding traffic.

   Source: Handbook p. 45

   “Going much slower than other vehicles can be just as bad as speeding. It is dangerous and you can be ticketed for impeding traffic.”
   South Dakota Driver License Manual, Handbook p. 45

5. When merging, try to enter at the same speed traffic is moving.

   Source: Handbook p. 45

   “When merging with traffic, try to enter at the same speed that traffic is currently moving.”
   South Dakota Driver License Manual, Handbook p. 45

6. Reduce speed to a safe speed before entering a curve.

   Source: Handbook p. 50

   “Always reduce speed before entering the curve to a safe speed”
   South Dakota Driver License Manual, Handbook p. 50

7. Reduce speed at the first sign of rain, snow, sleet or ice.

   Source: Handbook p. 50

   “Reduce speed at the first sign of rain, snow, sleet, or ice.”
   South Dakota Driver License Manual, Handbook p. 50

8. In a school zone with flashing lights or children present, obey the slower speed limit.

   Source: Handbook p. 61

   “In a school zone when lights are flashing or children are present, obey a slower speed limit.”
   South Dakota Driver License Manual, Handbook p. 61

9. Braking from 50 mph on dry pavement with good brakes can take about 158 feet.

   Source: Handbook p. 50

   “At 50 mph on dry pavement with good brakes, it can take about 158 feet.”
   South Dakota Driver License Manual, Handbook p. 50

Numbers to know

3 questions from the South Dakota practice test

1. 1. What habit does the South Dakota manual call the best way not to speed?

   1. Follow the fastest nearby driver
   2. Estimate speed from engine noise
   3. Check the speedometer often
   4. Look only at the posted limit once
   Show answer

   Check the speedometer often. South Dakota emphasizes that drivers are poor judges of their own speed, especially after leaving faster roads for slower streets. The manual’s practical answer is to check the speedometer often. Engine noise can mislead you because modern vehicles may feel smooth even above the limit, and traffic flow may also be speeding. The cue is transition: after an interstate, open highway, or long straight stretch, glance down repeatedly until your sense of speed matches the actual reading.

2. 2. What should you do when rain, snow, ice, or fog makes the posted maximum speed unsafe?

   1. Use the minimum speed sign as your target
   2. Drive exactly the posted maximum to avoid surprising others
   3. Reduce speed below the posted maximum
   4. Speed up until visibility improves
   Show answer

   Reduce speed below the posted maximum. A posted maximum assumes ideal driving conditions. South Dakota tells drivers to reduce speed when weather or roadway conditions make that maximum unsafe, including slippery surfaces or poor visibility. Driving exactly the sign number may look lawful, but it can still be too fast when traction or sight distance is reduced. Your cue is conditions, not just the number on the sign: if tires grip poorly or you cannot see clearly, slow before the vehicle needs sudden braking.

3. 3. In a South Dakota school zone with flashing lights or children present, what speed rule applies?

   1. Stop at every driveway
   2. Drive the regular limit unless a crossing guard is present
   3. Obey the slower speed limit
   4. Use the same speed as nearby traffic
   Show answer

   Obey the slower speed limit. The manual gives a direct school-zone instruction: when lights are flashing or children are present, obey the slower limit. Matching surrounding traffic is not enough if those drivers are failing to slow. The crossing-guard choice is incomplete because a guard can require stopping, but the speed duty exists when the lights flash or children are there. Use the cue of school-zone activity: flashing lights, children near the road, or a patrol signal mean your speed must drop.

Source: the South Dakota Driver License Manual, Safe Driving Tips. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.