Key points
On a wet road slow down about 10 mph; on packed snow cut your speed in half.
Source: Handbook p. 20
“On a wet road you should reduce your speed about 10 mph. On packed snow you should cut your speed in half.”
New Mexico Driver Manual, Handbook p. 20Bridges and overpasses can be icy even when other pavement is not.
Source: Handbook p. 20
“The pavement on bridges can be icy even when other pavement is not.”
New Mexico Driver Manual, Handbook p. 20Most tires grip a wet road up to about 35 mph; in heavy rain they can lose all traction at about 50 mph.
Source: Handbook p. 20
“most tires have good traction up to about 35 mph. However as you go faster, your tires will start to ride up on the water, like water skis. This is called “hydroplaning.” In a heavy rain, your tires can lose all traction with the road at about 50 mph.”
New Mexico Driver Manual, Handbook p. 20If you hydroplane, ease off the gas, keep the wheel straight, and do not stop or turn until the tires grip again.
Source: Handbook p. 21
“Ease your foot off the gas pedal. • Keep the steering wheel straight. Only try to turn if it’s an emergency. If you must turn, do it slowly, or you will cause your vehicle to skid. • Do not try to stop or turn until your tires are gripping the road again.”
New Mexico Driver Manual, Handbook p. 21At 50 mph it can take about 400 feet to react and stop; at 30 mph about 200 feet.
Source: Handbook p. 22
“At 50 mph, it can take about 400 feet to react to something you see and bring your vehicle to a stop. That is about the length of a city block. At 30 mph, it can take about 200 feet to stop.”
New Mexico Driver Manual, Handbook p. 22If you can see only about 200 feet ahead in heavy rain, snow or fog, you cannot safely drive faster than 30 mph.
Source: Handbook p. 23
“you may not be able to see much more than 200 feet ahead. When you cannot see any farther than that, you cannot safely drive faster than 30 mph.”
New Mexico Driver Manual, Handbook p. 23Use the four second sight distance rule: if you reach a fixed object before counting four seconds, slow down.
Source: Handbook p. 23
“If you reach the object before you finish saying “four-one-thousand,” you need to slow down.”
New Mexico Driver Manual, Handbook p. 23Watch for wildlife especially at dawn, dusk and the first few hours after dark, when many animals are most active.
Source: Handbook p. 21
“Be especially watchful for wildlife at dawn, dusk, and in the first few hours after darkness falls. Many animals are most active at these times.”
New Mexico Driver Manual, Handbook p. 21
Numbers to know
| Number | What it means | Manual |
|---|---|---|
| 10 mph | how much to slow down on a wet road | Handbook p. 20 |
| 35 mph | speed up to which most tires keep good traction on a wet road | Handbook p. 20 |
| 50 mph | speed at which tires can lose all traction in heavy rain | Handbook p. 20 |
| 400 feet at 50 mph | about how far it takes to react and stop | Handbook p. 22 |
| 200 feet at 30 mph | about how far it takes to stop | Handbook p. 22 |
| 4 seconds | sight distance rule count | Handbook p. 23 |
3 questions from the New Mexico practice test
1. On a wet road, about how much should a driver reduce speed?
- Only enough to match the posted maximum
- About 2 mph
- Exactly half at every speed
- About 10 mph
Show answer
About 10 mph. For wet roads, the manual gives a practical adjustment of reducing speed by about 10 mph. Cutting speed in half applies to packed snow, not ordinary wet pavement, and two mph is too small to account for the reduced grip. Matching the posted maximum ignores the need to adapt to surface conditions. The cue is water on the roadway before traction is fully lost: slow early, increase following distance, and avoid sudden steering or braking that could start a skid.
2. On packed snow, how should a driver adjust speed compared with normal travel?
- Maintain the posted maximum whenever tires have tread
- Reduce speed by about 10 miles per hour
- Cut speed in half
- Slow only to a crawl, as required for ice
Show answer
Cut speed in half. Packed snow calls for cutting speed in half because the tires have less grip and the vehicle needs more room to respond. The choice “Reduce speed by about 10 miles per hour” is the manual's approximate adjustment for a wet road, so applying it to packed snow understates the hazard. The choice “Maintain the posted maximum whenever tires have tread” ignores the need to adjust for slippery conditions, even when tires appear serviceable. The choice “Slow only to a crawl, as required for ice” is the instruction for ice, which is more severe than the packed snow guidance. Treat the surface as soon as snow is packed, reduce the normal speed substantially, and remember that the posted limit assumes better conditions.
3. With good tires, good brakes, and dry pavement, about how far may a vehicle traveling 50 mph need to react and stop?
- About 100 feet
- About 400 feet
- About 200 feet
- About 800 feet
Show answer
About 400 feet. The manual estimates about 400 feet for a vehicle at 50 mph to react to something seen and bring the vehicle to a stop when tires, brakes, and pavement are good. Two hundred feet is the listed stopping distance at 30 mph, so using it at 50 mph understates the space needed. One hundred feet is shorter still, while 800 feet is not the passenger-vehicle figure in this passage. Use visible stopping distance as a speed cue, especially near hills, curves, or blocked sight lines.
Practice this topic
Lock it in with safe driving questions from the free New Mexico practice test. Every answer comes with a plain English explanation.
Source: the New Mexico Driver 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.