V/Line’s strict heat restrictions along the Ballarat train service could be relaxed in the future after a new trail along the Geelong line allowed for boosted speeds in the peak of summer.  V/Line’s heat policy states that trains will slow their maximum speed from 160 km/h to 90 km/h on days where temperatures climb above 36 degrees.  Heat restrictions were applied to the Ballarat line for nine hours on Wednesday after temperatures between Deer Park and Bacchus Marsh exceeded 36 degrees, slowing seven services.  The line was also slowed back on December 18.  A V/Line spokesperson said a recent trial which had allowed Geelong trains to travel at 130 km/h during temperatures between 36 and 39 degrees would eventually be rolled out across the network.  “This is the first time in 20 years of heat-related speed restrictions that we have been able to increase safe travel speeds at these high temperatures,” the spokesperson said.  “Over time, we plan to roll out a similar approach to other areas of our network, including the Ballarat line, once we’ve carried out similar track improvements.”   Despite the changes along the Geelong line, train speeds will still be lowered to 90 km/h when the mercury heads past 39 degrees.  While the state government is in the process of rolling out a $551 million upgrade to the Ballarat line, improvements to allow trains to run at a higher speed during periods of high heat are not scheduled in the improvements.  Rail Futures Institute president John Hearsch, who worked as V/Line’s chief general manager of transport operations in the 1980s, said the restrictions which have been in effect since the 1990s were overly conservative.  “Where you’ve got high quality track and all components are in good condition and you’ve got a good monitoring system to ensure that any potential trouble spots are known and observed then the need to have restrictions in hot weather is far less,” Mr Hearsch said of the Ballarat line infrastructure.  “Most of the Ballarat line got a big upgrade as part of Regional Fast Rail project in 2005 and 2006 and provided that standard has been maintained then there shouldn't be a need for track of that quality to be slowed down. “The issue for V/Line is they wear the responsibility for safety and if anything goes wrong it’s on them.”