Bangalore to Goa based on what I heard from reliable sources:
First choice:
Bangalore -> Tumkur -> Kadoor -> Shimoga -> Sagar -> TaalGuppa -> Siddapur -> Sirsi -> Ankola -> Karwar -> Goa. (Aprox. 680km distanace)
Bad Stretches: Around Kadoor(30km), TaalGuppa(15km), once a while between karwar and goa so (Aprox. 75km distanace)
Second choice:
Bangalore -> Tumkur -> Kadoor -> Shimoga -> Sagar -> TaalGuppa -> Jog Falls -> Gerasappa -> Honnavar -> Kumta -> Ankola -> Karwar -> Goa. (Aprox. 640km distanace)
Bad Stretches: Around Kadoor(30km), Gerasappa(25km), Honnavar, Kumta, Ankola (40km) once a while between karwar and goa so (Aprox. 130km distanace)
Third Choice:
Bangalore -> Tumkur -> Chitradurga -> Haveri -> Sirsi -> Ankola -> Karwar -> Goa. (Aprox. 640km distanace)
Bad Stretches: Around Chitradurga, Davengere, Haveri, Sirsi (110km), once a while between karwar and goa so (Aprox. 130km distanace)
4th Choice:
Bangalore -> Tumkur -> Chitradurga -> Haveri -> Hubli -> Yellapur -> Karwar -> Goa. (Aprox. 700km distanace)
Bad Stretches: Around Chitradurga, Davengere, Haveri, Hubli (100km), Yellapur-Ankola Ghat (20km) once a while between karwar and goa so (Aprox. 140km distanace)
None of the route will give you even 90% good stretch.
I hope I am clear
Regards,
Ravi.