I think this will work best in a convertible:
Tilly is a 40lb dog.
We bought a box like this one
https://www.amazon.com/Ablechien-Dog...09MQJRTFP?th=1
And a kurgo harness for the car for safety
https://www.chewy.com/kurgo-tru-fit-...gaAn94EALw_wcB
I don't go more than 35mph with her with the top down but its so fun cruising