The N7 between J8 Johnstown and J7 Kill had been closed since yesterday for a technical examination of the crash scene but just recently has been cleared.
Diversions were in place, which were causing tailbacks on this part of the motorway.
Transport Infrastructure Ireland advised road users to use a different route and confirmed all lanes are affected between junctions 8 and 7 eastbound.
“Road closure due to a collision. All lanes affected,” it said in an earlier statement.
“Significant delays to your journey are likely to occur. Please use a different route for your journey.”
There has been a further crash near J5 along the M7 near Athgoe that is currently affecting eastbound traffic.
The collision on Saturday, involving a bus and a pedestrian, happened at approximately 3.30pm on Saturday afternoon.
A male pedestrian, aged in his 30s, was seriously injured after he was struck by a bus on the N7 motorway in Kill.
He was taken to Tallaght University Hospital for treatment and died as a result of the incident.
A post-mortem will now take place in due course, a garda spokesperson said.
The male driver of the bus, aged in his 30s, was not injured, while two passengers received injuries described as non-life-threatening.
Gardaí are now investigating the incident and appealing for any witnesses to contact them.
They are also calling on road users, who may have camera footage and were travelling in the area at the time of the collision, to make this footage available to them.
Three people have died on Irish roads in the last 24 hours in three separate road crashes.
Another pedestrian, aged in his 40s, was killed after being struck by a car on the R703 in Ballyroughan Big, Borris in Co Carlow yesterday.
Separately, a driver, aged in his 30s, died in the early hours of this morning after a single-vehicle crash on the L2107 at Cappadavock, Lavally, Tuam, Co Galway.