Many buses ply the route Malaysia-Singapore daily, you can probably find a bus every 15 minutes. These buses crosses the causeway into Johor Bahru.
Singapore Bus Service (SBS) buses and the Malaysian Causeway Link Yellow buses are available almost every 15 minutes. These buses takes you across the causeway to Johor Bahru (JB) or to the Larkin Bus Terminal, Johor.
The Causeway Link Yellow Bus picks passengers at the bus stop opposite the Kranji MRT Station in Singapore. This bus takes you to Sentral Kotaraya (City) Bus Terminal in Johor Bahru (JB) in Malaysia. Alternatively, take the SBS Transit Bus (a Singapore bus service) from Karanji or Queen Street in Singapore to the Sentral Kotaraya Bus Terminal, JB.
Other express buses crosses to Johor via the second link.
.............More at myMalaysiabooks.
