How can I make it easy for a player to select a choice at a rail junction?

So rail junctions are a nice simple way to pick between two destinations for incoming minecarts, however the challenge is making an easy way for the player to pick which direction they want to take as they approach the junction.

The simplest method is a button that they have to press while approaching the junction in the minecart:

Pressing the button causes the rider to switch onto the outbound track. Not pressing the button means they continue on the loop to the next junction. The problem here however is that the button is very hard to hit correctly while riding the rail at full speed.

What is an easier way for a player riding on a minecart to activate a junction so that they can take the alternate pathway? To be clear, the player should still have the option NOT to activate the junction and take the default path as well (as seen in the image above).

Solution 1:

Instead of a button you can use a trapped chest that the player needs to open; for this is much easier to hit. Another upside is that the chest closes automatically when the player gets out of range.

Solution 2:

The other answers are wonderful, but I have another option you may find useful. Stop the cart as in Linuxmint's answer, but use a repeater delay to automatically start it again after a short time if the user doesn't select an option. This allows cart riders who just want to stay on the default path to go AFK during the ride, yet still gives riders who want the alternate path plenty of time to push the button.

Here is a screenshot that shows what I mean. If the user does nothing, they will continue to the right. However, if they press the button, they will take the alternate route.