Ah, Good question!
This green arrow simply means that you have to go straight; in other words do not turn left or right.
If you have a regular green light you may be allowed to turn from the lane at the intersection. It’s kind of an extra reminder for drivers to “Go Straight Only!”
In this particular example, if you were to turn left you would be driving the wrong way down the freeway:
Hey, I’m Carmen, a being from Earth who has loved cars & driving for many moons. I became an ICBC GLP (graduated licensing program) driving instructor at the age of 22 in North Vancouver, Canada. The beautiful ‘North Shore’ was such a dream location. I’ve been working on this here website since 2012 when I created it.