Crematorium bosses say funeral services are still being disrupted by lorry drivers blocking the street after taking the wrong turn while using out of date satellite navigation systems.
Carmarthenshire council added warning signs, but the problem continues at Llanelli's Penprys Road even though the nearby road layout changed years ago.
A government summit is to be held to discuss similar problems around the UK.
But crematorium director Marjory Joplin says it is too late.
"There are millions of sat-navs out there that are being used that haven't been updated and a lot of people won't update because of the cost," she told BBC Radio Wales.
"It doesn't matter what the government does now... because they are already out there."
UK Local Transport Minister Norman Baker will host the talks in March to ensure everything possible is done to get the right vehicles on the right roads.
Carmarthenshire council said the issue of signage near the crematorium was being discussed again amid suggestions other languages could be used to warn foreign drivers the road was unsuitable for heavy goods vehicles.
In one week in September 2008 12 HGVs took the wrong turn towards the crematorium.
Additional roundabouts and road changes have been built in the area near Llanelli crematorium over the years so lorry drivers with out of date navigation systems take the wrong turn while trying to get to nearby industrial sites and factories.
"The council have been good enough to put up signs for us to tell lorry drivers that the factories they are looking for aren't there," she said.
"But because the lorry drivers are using sat navs that out of date - 10 years out of date - they are still coming to the crematorium and causing absolute mayhem on occasion."
A Welsh government spokesperson said officials have been in discussion with the Department for Transport and Highways Agency in England regarding solutions.
"We are considering options ranging from specific signing of unsuitable routes to producing maps that could be used by companies producing Satnav's for HGV drivers.
"The results of the summit will be considered with interest."