Customers want more trains to operate along the route
Fewer than half of passengers who use the rail line between Aberystwyth and Shrewsbury say they are happy with the number of trains running.
A survey of customers using the Cambrian line by rail watchdog Passenger Focus showed 41% were satisfied with the services on offer.
More than 800 passengers were quizzed by the watchdog on how the network should be developed.
Arriva Trains Wales said plans were in place to improve punctuality.
Results of the survey showed that as well as wanting more trains, in particular an hourly service on weekdays, customers wanted better punctuality.
The findings come as the Welsh Assembly Government invests £8m on the project while Network Rail funds the remainder of the money.
The improvements will be to the infrastructure and signalling on the Cambrian line between Aberystwyth and Shrewsbury.
This investment will make extra services feasible, but Passenger Focus's manager for Wales, Simon Pickering said to allow an hourly week day service additional funding would be needed from the Welsh Assembly Government.
"Our research shows there is a clear need for a more frequent service on this line as at the moment it isn't meeting passenger demands," he said.
"Regular, punctual trains are especially important to those passengers who don't have any other option but to travel by rail. Arriva Trains Wales must continue to work with the Welsh assembly to address this."
Arriva Trains Wales commercial director, Mike Bagshaw there were a number of actions in place to improve punctuality on the Cambrian Line.
"In the December timetable Arriva Trains Wales plans to run services through to Birmingham International which will not only provide improved journey opportunities but should have a positive impact on punctuality on the Cambrian Line," Mr Bagshaw said.
Gerwyn Jones from Cambrian Railways Partnership added: "An hourly train service between Aberystwyth and Shrewsbury would be a massive improvement to public transport provision in mid Wales.
"The flexibility and confidence afforded by an hourly service would greatly improve the attractiveness of rail travel for a wide ranger of journey purposes both within the region and beyond," he added.
Passenger Focus's research found 23% of passengers said they used the train because they did not have a car, and 28% said there was no other reasonable public transport option available.
The Cambrian Line runs between Aberystwyth and Shrewsbury
The research looked at passengers who used the train to commute, for business and leisure purposes.
The results show 71% of passengers were satisfied with their overall journey. The majority of passengers (60%) said they would prefer a faster journey rather than a train that stopped at more stops.
Stella Mair Thomas, Passenger Focus board member for Wales said it was a matter of concern that value for money fares continued to rate poorly with only 51% of respondents satisfied.
Results for security on the train (63%) and at the station (54%) scores were also too low, she said.
"The safety and security of passengers is of paramount importance.
"We will continue to stress the importance of having staff at the station. CCTV, lighting and help points all go a long way to make passengers feel safer at stations, but a staff presence is the one thing that really reassures passengers and is a deterrent to crime."