What is the difference between a green light and an all-direction arrow signal?

The traffic signals we usually see are the three-colored ones: green, yellow, and red. On the other hand, blue (green) arrows are also used to control the direction of travel. In some cases, you may see many blue arrows, and there are even traffic lights where left turn, straight, and right turn signals are all lit up. You might wonder how this differs from a green light at a crossroad intersection. This article explains the difference.

Does a green light not mean you can proceed with "peace of mind"?

A green light (green signal) usually means that you can "go straight, turn left, and turn right." This is also written in the Rules of the Road. However, as anyone who has actually driven knows, you cannot simply proceed unconditionally, especially when turning left or right.

At a typical intersection in an urban area, pedestrians will likely be crossing the crosswalk in the same direction, and there is a possibility that cars will come from the opposite direction, so when turning left or right, you must pay close attention to this traffic and, if necessary, stop along the way to wait for the other party (vehicle or pedestrian) to pass.

Arrow signals are more reassuring than green lights

On the other hand, for a blue arrow signal (blue arrow light), it is (almost) guaranteed that you can proceed in that direction with "peace of mind." This is because arrow signals are often introduced as pedestrian-vehicle separation systems.

A pedestrian-vehicle separation system is a method that separates the timing when pedestrian signals turn green from the timing when vehicle signals turn green to allow pedestrians to cross safely. Normal signals are not pedestrian-vehicle separation systems; both the pedestrian signal and the vehicle signal in the same direction turn green at the same time.

The most familiar one is likely the right-turn arrow signal. When the right-turn blue arrow is lit, traffic from the opposite direction is red for going straight, and the pedestrian signal is also red. (Incidentally, since the 2012 revision of the Road Traffic Act, U-turns are also permitted unless there is a regulation prohibiting them.)

There are also cases where only left-turn or straight-ahead arrows are lit, or where straight-ahead and right-turn arrows are lit at a T-junction.

When going straight and turning right are possible at a T-junction, the opposite direction is red. If the direction of travel allows going straight and the opposite direction is red, it is classified as a time-difference signal.

Be careful when turning left if only the left-turn and straight-ahead arrows are lit

As described, you can proceed with "peace of mind" with arrow signals, but the exception is the "right-turn vehicle separation system." (The reason I said "almost" guaranteed earlier is because of this system.)

The right-turn vehicle separation system is a method used at crossroads where only the left-turn and straight-ahead arrows are lit to prevent right turns, ensuring that vehicles do not conflict with oncoming traffic. By separating the timing for right turns, this is an effort to reduce accidents when turning right.

However, in this case, when the left-turn and straight-ahead arrows are lit, the pedestrian signal in the same direction is also green, so there is a possibility that traffic will conflict. Although the right-turn vehicle separation system is also classified as a type of pedestrian-vehicle separation system, it does not result in complete pedestrian-vehicle separation in this case.

With all-direction arrows, the opposite direction and pedestrians are red

Now, let's return to the first topic and talk about the case where an all-direction arrow is displayed. As for how it differs from a green light, you should already understand based on everything discussed so far.The difference is that 'both the opposing vehicle signal and the pedestrian signal are red,' so you can 'safely' turn left, go straight, or turn right (or make a U-turn), which is what it comes down to.

Since the opposing signal is red, this is a type of time-difference signal. In most cases where an all-direction arrow is installed, it is a 'pre-start' (early-start) system. (In places like Osaka, there are also locations where a regular time-difference signal turns into an all-direction arrow during the extension phase.)

A pre-start system means that when the green cycle begins, an all-direction arrow appears first, and then, once it switches to a normal green light, the opposing (delayed-start direction) vehicle signals and pedestrian signals also turn green. The term 'post-start' is used for the delayed-start direction.

By the way, for reference, another type of time-difference signal is the system where both directions are green at first, and the green light is extended for a while after the opposing signal turns red. This method is more common as a time-difference signal, and when people simply say 'time-difference signal,' they are usually referring to this type.

This method can be operated without extra cost because there is no need to change the signal heads to specialized ones. However, there are also types of regular time-difference signals that switch from a green light to an all-direction arrow signal.

This is because with the type of time-difference signal that extends the green light, it is difficult to tell that the opposing signal has turned red, and one must observe carefully, such as checking how much time has passed since the pedestrian signal in the same direction turned red.

However, under the Road Traffic Act, a green arrow is not defined as having any differentiation such as being able to travel with priority compared to a green signal, so please be aware that you should drive safely while exercising caution in the same way.

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In places like Tokyo, at large intersections where time-difference signals are installed, dedicated right-turn signals are installed to compensate for the lack of clarity.

'Pre-start' time-difference signals are not recommended

Incidentally, the National Police Agency indicated its operational policy for time-difference signals in the guidelines for the operation of time-difference traffic signals revised in 2008 (Heisei 20), titled 'Establishment of Operational Guidelines Concerning Control by Time-Difference Signal Indications (Notification)'.

According to this, the 'pre-start' type at standard crossroads is to be avoided because 'there is a risk of collision with oncoming straight-through traffic from the delayed-start direction while right-turn traffic is continuously passing, and there is a risk of drivers in the delayed-start direction starting based on assumptions.'

In addition, it is also stated that all-direction arrow signals 'represent the same meaning as a green light, and displaying them in two different ways at the same intersection is likely to cause confusion for drivers, so it should not be done.'

Therefore, it is estimated that this method will decrease in the future.

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