The state I live in allows adolescent to drive at the age of 16 years. I have mixed feelings about this. Since you asked for reason why the legal driving age should be raised to 18 that is what I will discuss.
As many know, the adolescent brain at the age of 16 is still in major development mode. Of significant importance is the development of the frontal lobe. This area of the brain assists in inhibition, concentration, attention and multitasking. Although this area is developing, it still displays some weaknesses. Many have observed the spontaneity of adolescents. Their tendency to act without thinking first and never worrying about consequences. This is my main concern for adolescent drivers.
In the state that I live in a 16 year old can only have one other person in the car with them for the first year that they have their drivers license. I think that this is positive because it is less distracting for the driver. It makes it illegal for them to pile 4 or 5 of their friends in the car. If they break this rule, they lose their license for a certain amount of time.
I personally believe that 16 is too young for anyone to drive, no matter what state they live in. Eighteen is a good age for many reasons. An eighteen year old is generally more mature than a 16 year old. They are ready to go to college, work, and start their adult lives. I do not think a 16 year is ready for this.
I agree with the premise of raising the age everywhere, of course, I'm not 16 or 17 anymore (by a longshot). I might feel differently if I was.
Many European countries already have an age limit. For one, this takes cars off the road, which is never a bad thing for both the environment and traffic control. But Europe also has much better public transit and much smaller land mass to deal with.
In Hawaii specifically, and I've only been there twice, mind you, traffic was pretty bad in and around Honolulu, where the bulk of the state's population is. The road system they have there was never designed for the number of vehicles it currently handles, in my opinion.
As a teacher, I like the idea of not having students younger than seniors driving to school each day. It eases parking issues, but also, a sophomore in high school is easily distracted behind the wheel, especially with friends in the car.
You could argue this pretty much the same way you would argue it for any other state.
What I would start with is the idea that younger teens are responsible for a much higher percentage of car crashes than they should be (given how many of them drive compared to people of other ages). I would point out that kids of that age are not yet all that mature and may tend to make really bad choices that they would not make when they are older.
Specific to Hawaii (or at least to Honolulu) you could argue that there is less of a need for teens to drive in Hawaii because of how compact the city is and how good the bus system is (or at least was when I lived there). But, on the other hand, that's not going to do you much good if you live out in Nanakuli or Laie...