Seeing, Communicating, and Speed Control Cheat Sheet - Quick Reference Guide
Quick reference for exam-critical information from Sections 2.4-2.6: the 12-15 second rule, mirrors, signaling, stopping distance formula, and speed adjustments.
The 12-15 Second Rule
| Speed | Look Ahead Distance |
|---|---|
| City/low speed | 1 block |
| Highway speed | 1/4 mile |
Key: Look 12-15 seconds ahead and shift attention near and far.
Stopping Distance Formula
Perception + Reaction + Braking = Total Stopping Distance
At 55 mph (MEMORIZE)
| Component | Time | Distance |
|---|---|---|
| Perception | 1¾ seconds | 142 feet |
| Reaction | ¾-1 second | 61 feet |
| Braking | — | 216 feet |
| TOTAL | — | 419 feet |
Remember: 419 feet > football field (360 feet)
Speed vs. Braking Distance
Braking distance = Speed² (squared)
| Speed Change | Braking Distance |
|---|---|
| 2x speed | 4x longer |
| 3x speed | 9x longer |
| 4x speed | 16x longer |
Weight Effect on Stopping
| Vehicle | Stopping Distance |
|---|---|
| Loaded truck | Shorter (more traction) |
| Empty truck | LONGER (less traction) |
Exam Trap: Empty trucks need MORE distance to stop, not less!
Speed Reductions for Conditions
| Condition | Reduce Speed By | Example (55 mph) |
|---|---|---|
| Wet road | 1/3 | → 35 mph |
| Packed snow | 1/2 | → 27 mph |
| Ice | Crawl | Stop when safe |
Wet roads DOUBLE stopping distance
Slippery Surface Warnings
| Condition | Why Dangerous |
|---|---|
| Shaded areas | Stay icy after open areas melt |
| Bridges | Freeze BEFORE roads |
| 32°F temperature | Ice forming danger zone |
| Black ice | Looks wet, actually ice |
| Just after rain starts | Oil/water mix very slippery |
Quick Ice Check
Feel mirror, mirror support, or antenna—ice there = ice on road.
Hydroplaning
| Fact | Value |
|---|---|
| Can occur at | 30 mph |
| Risk factors | Low tire pressure, worn tread |
| Response | Release accelerator, push clutch, DON'T BRAKE |
Mirror Rules
Adjustment
- Check before every trip
- Adjust with trailer straight
- Show some part of vehicle as reference
Convex Mirrors
- Show wider area
- Objects appear smaller and farther than actual
Lane Change Mirror Checks
- Before signaling
- After signaling (blind spots)
- During lane change
- After completing change
Signaling Rules
Turn Signals - Three Rules
- Signal early (before turn)
- Signal continuously (during turn)
- Cancel signal (after turn)
Lane Changes
- Signal BEFORE changing
- Change slowly and smoothly
Brake Light Warnings
Flash brake lights when:
- Trouble ahead others can't see
- Making tight turns
- Stopping on road
- Driving slowly
Never direct traffic or signal others to pass
Emergency Warning Devices
Placement Time
Within 10 minutes of stopping
Divided/One-Way Highway
- 10 feet from vehicle
- 100 feet toward traffic
- 200 feet toward traffic
Two-Lane Road
- 10 feet from front/rear
- 100 feet behind vehicle
- 100 feet ahead of vehicle
Near Hill/Curve
Place rear triangle visible from 500 feet
Curves
- Slow BEFORE entering
- Don't brake IN curve (causes skid)
- Use gear allowing slight acceleration
- Trucks can roll at posted curve speeds
Visibility Rule
Always be able to stop within the distance you can see.
- Fog/rain → slow down
- Low beams → slow down
- Night → slow down
Communicating Presence
| Situation | Action |
|---|---|
| Passing others | Light horn tap |
| Hard to see (dawn, dusk, rain) | Low beam headlights |
| Parked on roadside | Four-way flashers |
Key Numbers to Memorize
| Item | Number |
|---|---|
| Look ahead time | 12-15 seconds |
| Look ahead (city) | 1 block |
| Look ahead (highway) | 1/4 mile |
| Perception at 55 | 142 feet |
| Reaction at 55 | 61 feet |
| Braking at 55 | 216 feet |
| Total at 55 | 419 feet |
| Double speed = braking | 4x |
| Triple speed = braking | 9x |
| Wet road speed cut | 1/3 |
| Snow speed cut | 1/2 |
| Warning device time | 10 minutes |
| Triangle distances | 10, 100, 200 feet |
| Hydroplaning speed | 30 mph |
| Hill/curve visibility | 500 feet |
Quick Quiz
Q: Total stopping distance at 55 mph?
A: 419 feet
Q: Double speed = what braking distance?
A: 4 times longer
Q: Empty or loaded truck stops faster?
A: Loaded (more traction)
Q: Wet road speed reduction?
A: Reduce by 1/3
Q: Warning devices placed within?
A: 10 minutes
Q: Hydroplaning can occur at?
A: 30 mph
Q: Convex mirrors make things appear?
A: Smaller and farther away
Q: When to slow for a curve?
A: BEFORE entering (not during)
Next Steps
- Memorize stopping distance at 55 mph: 419 feet
- Know speed-squared rule: 2x speed = 4x braking
- Remember: Empty trucks stop SLOWER
- Speed reductions: 1/3 wet, 1/2 snow
Ready to test your knowledge? Start practicing with our Speed and Space questions.