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Traffic lights warningUnited States

An introduction to the traffic rules and road signs of United States. Learn about driving, road safety and much more in our illustrated book, with answers to frequently asked questions.

For informational purposes only. Always follow official regulations. Some content and images were created with AI assistance.

Traffic signs
Traffic rules
United States

40. Traffic lights warning

A traffic lights warning is a warning sign that alerts drivers that traffic signals are located ahead. It is commonly used where the signals may be unexpected, difficult to see from a distance or located on a road where drivers need additional time to prepare to stop.

Drivers approaching a traffic lights warning should reduce speed when necessary, watch for the signals ahead and be prepared to stop if the traffic light changes or traffic is waiting at the intersection.

Traffic lights warning
Traffic-lights warning sign on Mountain View Road near Bear Tavern Road. (Ewing Township, New Jersey, United States)
Wikimedia.org • Famartin • CC BY-SA
How are traffic lights ahead warned of in the United States?

The US MUTCD identifies a yellow diamond-shaped Signal Ahead (W3-3) sign. It is installed where a signal cannot be seen soon enough for a driver to respond, and may also be used for extra emphasis. It does not itself order a stop.

🔗 mutcd.fhwa.dot.gov • FHWA MUTCD11th Edition including Revision1 December2025 — relevant regulatory/warning/guide, marking and signal provisions

Does a traffic-lights-ahead warning require an immediate stop in the United States?

No. A warning sign is not an automatic STOP instruction and does not create a new numerical speed limit. Reduce speed when necessary, look for a queue or a concealed signal, and obey the traffic lights and any separate speed or stop signs.

🔗 mutcd.fhwa.dot.gov • FHWA MUTCD11th Edition including Revision1 December2025 — relevant regulatory/warning/guide, marking and signal provisions

What should you check if the next traffic lights are difficult to see in the United States?

The Signal Ahead warning is especially relevant where signal visibility is restricted by a bend, a crest or another obstruction. Scan for queued traffic and a red light; follow the actual signal and posted speed restrictions.

🔗 mutcd.fhwa.dot.gov • FHWA MUTCD11th Edition including Revision1 December2025 — relevant regulatory/warning/guide, marking and signal provisions

1 United States 2 Motorway 3 Expressway 4 Speed limit 5 Minimum speed 6 Advisory speed 7 Bike path 8 Pedestrian warning 9 Tunnel 10 Bridge 11 Speed bump 12 Toll road 13 One-way traffic 14 Slope 15 Bus lane 16 Bus stop 17 Dead end 18 Stop sign 19 Give way 20 Roundabout 21 Road narrowing 22 Pedestrian crossing 23 Railway crossing 24 Mandatory direction 25 Turn prohibition 26 School area 27 Crossing animals 28 Slippery road 29 Rockfall 30 Aircraft 31 Curve 32 Chevron 33 Wrong-way driving 34 Roadworks 35 Height limit 36 Weight limit 37 Radar speed sign 38 Selective barriers 39 Traffic lights 40 Traffic lights warning 41 Pedestrian lights 42 Road markings 43 Bike box 44 Speed feedback 45 Driving licence 46 Traffic mirror 47 Emergency telephone 48 Cycling route 49 Parking 50 No parking 51 No stopping 52 Parallel parking 53 Park and ride 54 Kiss and ride 55 Disabled parking 56 Traffic management 57 Reversing 58 U-turn 59 Carpool 60 Detour 61 Uncontrolled crossroad 62 Ramp 63 Exit 64 Horse riding 65 Emergency exit 66 Runaway truck ramp 67 Oversize load 68 City limit 69 Tourist attraction 70 Horn 71 Axle weight limit 72 Licence plate 73 Charging station 74 Flooding 75 Dip 76 Horse 77 Local traffic 78 Pedestrian 79 Cyclist 80 Motorcycle 81 Truck 82 Bus 83 Police 84 Ambulance 85 Police signals 86 Gravel road 87 Pothole 88 Median strip 89 Public property 90 Path 91 Particulates 92 Air pollution 93 Interchange 94 Rush hour 95 Filling station 96 Road code 97 Two-way traffic 98 Passing lane 99 Street gutter 100 Road debris ...