He was speaking after the launch of the ‘Enough is Enough’ campaign group on Monday night.
An SDLP delegation attended the event, where speakers included relatives of those who had lost their lives on the road.
West Tyrone MLA Mr McCrossan said: “Since becoming an MLA I have relentlessly campaigned for this vital upgrading work to be carried out on the A5 road and it has been a sense of deep frustration for both myself and people locally that we are still fighting all these years on.
"Those who have opposed this project have caused considerable damage and I would ask them to come forward and meet those affected so they can understand the need for this project.
“I welcome the launch of the Enough is Enough campaign and applaud their efforts in bringing people together to highlight just how important this issue is. In the coming weeks and months I will be meeting with a variety of stakeholders, including church and business leaders to ask them to lend their support to our efforts to see this project completed."
SDLP Mid Ulster MLA Patsy McGlone added: “After attending the Enough is Enough launch on Monday night it was clear to see the strength of feeling that exists around this vital road upgrade.
"The human cost of the delays to this project were laid bare in the moving testimonies of those who lost loved ones killed on the A5. There was also real positivity that coming together and community action would bring real momentum to the campaign to see this work carried out.
“This work will not only benefit people locally, it will make a difference to the lives of people on both sides of the border and those from right across the North who travel this road regularly for a variety of reasons. The SDLP has long been calling for this work to be carried out and we will stand firmly behind the campaign until this life-saving project is delivered.”