Well the rosary is primarily a vocal prayer so it is not surprising you pray it out loud, I do too except when I am out in public. I merely can pray it in my head. You (plural - meaning people) can pray out loud whilst a back train of thought/mental prayer goes through their head. To pray it in your head and mediate at the same time, well I dont know. I am not a healthy person, so my brain can’t do that. I say the decade and then meditate on the mystery, other people do it other ways. At this point one meets God and it can be a long meditation or just a little musing. Don’t take too much notice of my words I am not saying the rosary is meditative , it is vocal but can be used to meditate on, because it is based on scripture. Think of it as a lecito divina of sorts, reading the scriptural passage/ mystery in question and then mediating on it by lifting it to God in prayer. The Hail Mary’s I find make quite a meditative feeling whether said out loud or in ones head as you are saying them to Our Lady who is no doubt listening and helping guide you and has taken note of whatever intentions you have prayed for for that decade and is interceding for you on whatever graces you have asked for for that decade so whilst saying the Hail Mary’s it can happen that an answer or message can come to you. As for second part, I did not mean to make you think there is a non meditative or meditative rosary, there isnt as I said about, it’s a vocal prayer primarily, but a person can say it in a meditative way. I initially say I am a meditative sayer of the rosary, meaning it is me who is the doer not the rosary . You can say it without thinking or meditating on the mysteries at all and then it is pretty much purely vocal. You should still offer intentions and ask for graces though. I am not good with words sorry for the misunderstanding, it is my wonky brain. I am sorry I can’t comment on the driving issue, I think you should be careful and concentrate on driving but you are the one who should decide.