The Kerala and Karnataka Expresses
The KK (Karnataka-Kerala) Exp. was introduced in 1976 from New Delhi to Trivandrum and Bangalore, the train bifurcating at Jolarpettai. The train was later (1980?) split into two trains, the Kerala Exp. running New Delhi - Trivandrum and the Karnataka Exp. running New Delhi - Bangalore. The Kerala Exp. then split at Palghat with one portion going to Mangalore. The Karnataka later changed to take the Gooty-Secunderabad-Nagpur route. The Karnataka later ran with three different routes on different days of the week: through Renigunta and Vijayawada; through Wadi and Secunderabad; and through Wadi and Manmad.
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Kerala Exp. overlapped with the Jayanti Janata which bifurcated at Shoranur with one part of the train going to Cochin Harbour and the other to Mangalore. Later, these two trains were merged to form the Kerala Mangala Exp. Later yet (1990?), a separate train to Mangalore was introduced named the Mangala Exp. (Nagpur-Vijayawada-Coimbatore-Palghat-Shoranur). With the opening of Konkan Railway, the Mangala was renamed the Mangala-Lakshadweep Exp. and extended to to Ernakulam (Jhansi-Nasik-Panvel-Kankanadi-Calicut-Shoranur).
Originally the TN, AP, and KK (Karnataka-Kerala) Expresses were three trains sharing the same scheduling slot and much of their routes. After the KK was split into two trains, the Kerala and the Karnataka Expresses and the four trains were distributed in two scheduling slots, with the Kerala and Karnataka being in different slots. Later yet, each train got its own slot.