A traffic island at the intersection was removed by contractors this week, to make the Anzac Ave approach on to Castle St more like a T-intersection.
NZTA Otago Southland operations manager Roger Bailey said the agency was concerned motorists were not stopping at the intersection before turning into Castle St, which was part of the state highway network.
"We've been watching it and observing what's going on. It's quite a concern that people aren't stopping there, so we wanted to reinforce everything a bit better," Mr Bailey said.
Traffic cones had been in place for the past month, but provided a relatively "flimsy" barrier, he said.
Water-filled barriers would be put in place as part of the strengthened temporary control measures.
"They are more robust and visible to motorists. Basically, we are improving the temporary arrangement, and we still have all the process to work through to come up with a permanent solution," Mr Bailey said.
Work was done at the NZTA's cost and would be completed in a few days, weather depending.
The intersection's closure was one option considered by the NZTA, DCC and road user groups.
The NZTA had studied the intersection since the death of Dunedin cyclist Peter James Wells (55), who was hit by an empty logging truck there last November.
