Traffic Lights
Traffic Lights
This comic is an animated gif which features an array of traffic lights which are lighted signals posted at intersections to control vehicular traffic. The standard North American traffic light has three solid lights: red, yellow and green (meaning, in simplistic terms, "stop", "warning: the light will be changing to red" and "go" respectively). More complicated lights sometimes have additional signals such as arrows indicating go or stop for a specific direction such as left or right turns.
However, as in the strip, sometimes an intersection has multiple lights with certain of them designated to apply solely to a specific lane or specific direction of travel. A common one is a left-turn light that allows the lights to stop or allow left-turn traffic independent of the rest of the traffic. Another common example is a light that applies only to public transit like streetcars that run on tracks on the city streets.
There are also other rules and features that tend to be unique to different localities as noted in the Wikipedia article for Traffic-light signalling and operation .
In this comic, Randall is commenting on the confusion that can be caused by having too many lights with multiple rules attached by creating an exaggerated example.
In this strip, the right light has a sign indicating that the light and the right lane are for left turners, while the 3rd-from-left is a straight or right turn lane and the 2nd from left is right turn only. In normal course, right turns would be permitted from the right lane and left turns from the left lanes. The system in this comic would have turning traffic crossing each other, as well as the straight-ahead traffic and would cause chaos (and require very complicated traffic light phases to control). The left-most light on the post has a sign indicating that left, right and straight travel are all prohibited, which is even more confusing.
The comic, as an animated gif, cycles through various phases, at first appearing somewhat normal, but then adding unusual phases. The animated gif takes about 90 seconds to cycle through the 32 discrete panels before repeating. The left post light has (unusually) left and right arrows, later becoming up and down arrows. At times the light completely shuts off, and at other times, has conflicting signals.
The third-from-left light has red and yellow, and later all three lights come on at the same time, then all three lights go yellow, and then reverse with green at top and red at bottom. The bottom light then becomes an arrow.
The fourth-from-left traffic light switches from a green light to a purple light at times.
The right light only lights red in each position.
The second-from-left light and second-from-right lights do not appear to have any quirks other than changing phases in unusual patterns.
At frames 21 and 22 (see below) the colors of the latter five lights correspond to the color sequence of the letters in the Google logo. Only the first letter of the logo, which is blue, is not reproduced on the first traffic light.
The title text mentions a straightforward intersection that allows going forward but not turning. Even though Randall is confused, in some places, a red light and a forward green arrow permits going forward but disallows turns.
The following is a breakdown of all of the frames of the animated gif comic.

The following is a closeup on the lights, and the bird. The lights from left to right are here shown top to bottom. Time advances to the right.

Originally, the second light had a couple frames near the start that were different. The closeup of this was as follows:

