I know the newer RTxx15 radars can make announcements because they have bluetooth and a separate Varia application. @GPLama (Shane Miller) has a great video on why and how to do this (www.youtube.com/watch, I have an RTL510 that works great and I don't plan to replace it.
The Explore 2 has better alerts than my older 520. When I pair the RTL510, I can go into Sensors | Radar | Sensor Details | Alert Settings. There, I can set it to Multi Tone. When a car is approaching, there are 3 beeps. They are louder than on my 520 but can still be hard to hear depending on the road surface.
What I'd like is to have a spoke audio alert since I ride with open ear headphones. In the past, I found posts that said Garmin shouldn't add spoken announcements for safety reasons (i.e. you shouldn't ride with headphones). @GPLama does a great job of explaining how and why you can use headphones safely.
Here's what I don't understand... First, I can set my Explore 2 to make spoken announcements through my headphones for many reasons including lap summary statistics and upcoming turn directions. Second, the Explore 2 can provide a beep when a car approaches. Why can't there be an option that optionally allows me to hear "Car approaching" or "Fast Car Approaching" through my headphones? Clearly the capability is there to combine these two and greatly enhance safety on the road.