Why U.S. Stoplights Sway—and German and UK Signals Stand Still

Written By dKay in Maine

Yesterday was one of those days, blue-ish sky, but windy—at least in the area I live in. Nothing major, just windy enough to make leaves spin and traffic lights rock on their cables and mast arms. While that’s an ordinary sight in Maine, it still amazes me after years with pedestal-mounted lights in Germany and the UK. Initially, I only wanted to make a light-hearted post about this (hint: I might have uploaded a video on TikTok), but it wasn’t me if I wouldn’t dive into the bigger picture: different networks, design philosophies, and laws that shape how we place, sequence, and even see traffic lights. This post compares these systems and explains why a signal in the U.S. may sway while one in Munich or London remains steady.

Why Some Lights Hang and Others Hug the Curb

In the U.S., a 1,161-page-long document, the Manual on Uniform Traffic Control Devices for Streets and Highways establishes “uniform national criteria for the use of traffic control devices that meet the needs and expectancy of road users on all streets, highways, pedestrian and bicycle facilities, and site roadways open to public travel.” In short, it establishes rules for various things, including road signs, street name signs, recreational signs, and traffic lights. It steers designers toward conspicuous, often overhead placement—such as span wire or long mast arms—especially on multi-lane or higher-speed approaches.

Guidance highlights the safety benefits of far-side, overhead primary faces, leading agencies to often align on overhead installations when it comes to fast or wide approaches. That geometry delivers long sight lines across large intersections, but it also means you’ll notice the wind.

By contrast, the UK’s 200-page-long Traffic Signs Manual: Chapter 6 treats post-mounted primary and secondary heads as the norm; a secondary head across the junction is usual, but full gantries or overhead mounting are the exception. The effect in the streetscape is tidier, lower-profile hardware that rarely moves.

Germany’s 88-page-long planning guideline RiLSA sets a similar baseline: signal heads are installed on masts or mast arms, with gantries or suspension only “in some cases”—explicitly noting the strong visual impact of gantries in urban settings. Additionally, Chapter 6.4 states that “the primary signal is generally positioned on the right-hand side of the road, while duplicate signals can be positioned on the left-hand side and/or over the carriageway.”

And it’s not only the right-hand side, it’s also in close proximity to the stop line—another difference to traffic lights in the U.S., where the lights are usually on the opposite side of a junction. Just like in the other countries, if not all lanes on the approach to an intersection are given right of way at the same time, there must be at least one signal head (with arrows) for each signal-controlled turning movement and at least two signal heads for vehicles going straight ahead.

The “Get-Ready” Stage: Rot-Gelb (DE), Red+Amber (UK), and Why the U.S. Skips It

The phase sequence that drivers see is another clear difference. In the UK, the Highway Code spells out red → red+amber → green (with red+amber meaning ‘Stop,’ but prepare to go when green shows), and amber alone means stop if it’s safe to do so. Germany’s StVO § 37 defines the same Rot-Gelb (“Red-Yellow”) “get ready” stage before green.

The U.S., by contrast, changes indications singly, so you go directly from red to green. At this point, I also want to note that manual transmissions are far more common in Europe than in the U.S., and the red-yellow phase allows those using a manual transmission to be ready once the light changes to green.

A side-by-side comparison of U.S. and UK traffic lights switching from red to green.

A little fun fact (well, more fun than fact): A German driver might state that the traffic light was “kirschgrün”—“cherry-green” after they passed a traffic light that was just on the brink of turning from yellow to red. However, keep in mind that that’s slang and it’s not a legitimate excuse in traffic court. The rule is that a driver must stop when the light turns yellow, as long as they can bring their car to a complete stop with moderate braking and without putting those behind them in danger.

Permissive, Conditional, or Prohibited: Three Legal Cultures at the Light

Another stark difference becomes apparent when looking at the ‘turn on red’ rules. In most (not all) of the U.S., right turn on red is permitted after a full stop unless a NO TURN ON RED sign prohibits it. On the other side of the Atlantic, Germany takes the opposite default: no right on red unless a site has the small Grünpfeil (“green arrow”; pictured below) plate, which authorizes a right turn on red after stopping. That exception is codified directly in StVO § 37. The UK keeps it simple: no turns on red; drivers wait for a green or a green arrow.

Designed to Sway: Wind, Vibration, and How Agencies Manage Movement

And about that swaying. Overhead structures are designed to move. Research compiled by FHWA and the National Cooperative Highway Research Program documents wind-induced vibration mechanisms—especially galloping on flexible mast arms carrying signal heads and backplates. In certain wind conditions, tip movements can appear dramatic from the sidewalk but are a known, engineered behavior that agencies manage through detailing, inspection, and (when needed) vibration-mitigation devices. But in all honesty, I will probably never stop being amazed by it, hoping that the arm won’t rupture or the wire(s) won’t snap.

Not Better, Just Fitted: What Signals Reveal About Each Country

Step back and the contrasts tell you as much about roads as about signals. The U.S. builds for wide lanes and long sight distances, so designers favor big, overhead, lane-aligned faces, permissive right-on-red (with local exceptions). The UK and Germany lean toward compact, post-based equipment that keeps the skyline clear and fits the often narrower, centuries-old streets.

While some of my readers might criticize me for this, I would say that neither approach is inherently “better”; each fits the geometry, speeds, and norms that have been established. Which is to say: a signal that sways in Portland, Maine, and one that stands still in Munich aren’t contradictions—they’re design philosophies made visible. However, I appreciate the fact that the traffic lights in the U.S. are easier to see from within the car, but it might still take another couple of years for me to get used to the ‘American Sway.’

dKay in Maine
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