Public transport users have criticised construction on the Ballarat line upgrade, with the planned train line duplication falling a kilometre short of a previously created loop.

A three-kilometre stretch of track will be duplicated between Bacchus Marsh station and Kerrs Road, but the state government has confirmed there will be a gap to the Rowsley loop, built in 2016.

The duplication allows for trains going in opposite directions to pass one another without causing delays. Earthworks on the upgrade began last month.

Public Transport Users Association Ballarat convener Ben Lever said not connecting the loops was “illogical”.

“The point of the project is to get rid of these bottlenecks, but having one kilometre of single track between loops makes it so much more complicated to timetable,” he said.

“Timetabling will be hard, in particular, when one train is late and they need to be in specific spots at specific times.

“It’s just really disappointing and seems illogical that you’d duplicate and get in sight of the Rowsley loop and not link them up.

“If it’s a long stretch it’s understandable, but it’s only one kilometre.”

Regional Rail Revival project director Mark Haryvluk said detailed assessments had been carried out to determine where track duplication would take place.

Mr Haryvluk said the placement would allow trains to come out of nearby stabling facilities and would enable the delivery of extra peak services and trains every 40 minutes during off-peak periods.

The full upgrade is expected to be completed next year.