Trivandrum to Kanyakumari by car
Thiruvananthapuram is in Kerala and Kanyakumari is in Tamil Nadu state. Both places are popular tourist destinations and most visitors to Trivandrum do not go back without visiting Kanyakumari.
The best route from Trivandrum to Kanyakumari is via NH 66, which is pretty much a straight high way. However, this is a state high way and the roads are narrow with no median in most places. You won't be able to drive fast and over taking other vehicles also would be a challenge in many places. In many places, this state high way looks like local road.
See the route from Trivandrum to Kanyakumari in Google Map:
Public transport buses
Kerala State Road Transport Corporation (KSRTC) operates buses from Thiruvanthapuram to Kanyakumari and this is the cheapest mode of transportation. As of July 2016, the ticket rate in KSRTC is Rs 70. Running time for KSRTC buses is 2.5 hours.
Book KSRTC bus tickets to Kanyakumari here - http://www.ksrtconline.com/KERALAOnline/.
Multi-axle A/C buses from Trivandrum to Kanyakumari
There are plenty of private luxury buses operating services between Trivandrum and Kanyakumari and they are probably the fastest way to reach your destination. Most of these buses have a running time of about 2 hours to reach Kanyakumari.
There are many multi-axle A/C semi-sleeper buses operate between these places. Average ticket rate in such buses is Rs 250 to Rs 300, depending on the season and schedule. Most of these buses start early in the morning at about 6 AM. You can search for buses in private bus ticket booking websites like redBus.in and yatra.com
Nearest airport to Kanyakumari
Located at 93 km distance, Trivandrum International airport is the nearest airport to Kanyakumari. From the airport, you will have to depend on buses or car to reach Kanyakumari. Apart from well connected with other major cities in India, this airport is connected with foreign countries like Singapore, Dubai etc. All major airlines have offices and operate domestic/international flights to Trivandrum.
Trains to Kanyakumari
Well connected by Indian Railway network, Kanyakumari can be easily reached via trains. There are direct trains from major cities like Chennai and Bangalore. Since this is a short journey of less than 2 hours, there is no advance reservation necessary, unless you are travelling long distance to other destinations. You can buy train tickets from the local railway station.
Kanyakumari is in my lens as a place to visit. I'll be driving down to Ernakulum after the monsoons. Let me know how is the road condition south of Shertallai? AFAIK, the roads are narrower towards the south side?