National Highways is also offering people the chance to join live web chats about the project or call in during telephone surgeries.
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The improvements to this busy urban motorway will ease congestion, increase capacity and enhance safety.
National Highways Project Manager James Finnigan said:
“Road users and residents will have seen us carrying out preparatory work since the middle of June and we're due to start work in earnest in August.
“The M621 is a vital link between Leeds city centre and the surrounding road network. During peak times, as many motorists will know too well, traffic often becomes very congested between junctions 1 and 6. We need to create more reliable journeys for everyone using this route, making sure more people get to where they need to go safely.
“It’s great news for the local and regional economy as our scheme will support economic growth aspirations – helping people and businesses access Leeds city centre and the surrounding area.”
Once complete, the upgrade is expected to boost economic growth by shortening journeys, traffic flow at peak times and average speeds.
The scheme will create additional lanes at the junction 2 roundabout and junction 3 westbound, as well as between junctions 1 and 3 where two short lengths of the existing hard shoulder will be converted to additional lanes for traffic.
Changes will also see improvements to junction 3 westbound, giving priority to the main M621 traffic, allowing it to flow more freely.
The junction 2a exit slip road will be permanently closed, reducing the risk of collisions resulting from the short distance between junctions 3 and 2a.
Initial work will also include the installation of new average speed cameras, overhead electronic information signs and changes to the road layout to help traffic movements around junctions 2 and 3.
Narrow lanes and traffic management will be introduced to keep road users and roadworkers safe during construction, while maintaining the maximum capacity for traffic.