New restrictions are to be introduced on the A58 Halifax to Wyke route and at Aachen Way, King Cross, Halifax.
Council highways and road safety bosses say the stretches have seen a marked increase in traffic.
A 30mph speed limit will be imposed at Aachen Way towards the King Cross junction.
The speed limit on the A58 from Stump Cross to Hipperholme will be reduced from 60mph to 50mph following a number of crashes and beyond the Hipperholme crossroads the limit will be reduced from 40mph to 30mph.
The changes will take effect in the next six to eight weeks as part of a five-year plan to reduce accidents across the district.
David Brown, team leader for traffic at Calderdale Council, said: "We have a local safety programme where specific communities are targeted for roads that have known problems.
"The plan is to enforce changes, educate the public and engineer plans for improvement."
Peter Shepherdson, road safety officer, said: "While the amount of traffic has changed over the years, the speed limits have not.
"Residents' needs should be balanced with those travelling in and out of the area. It is hoped that the changes will mean a third fewer people injured on the roads."
Drivers had mixed views about the changes.
Office worker Julie Smailes, 38, of Bramley Lane, Hipperholme, said: "I use this road every day and I think when the changes are made it will just make the roads worse."
John McBride, 30, a project manager from Thompson Close, Hipperholme, said: "I think this is just going to steer people away from Halifax. You already have the problem with parking and it will just become a no-go area if it is harder for people to get into the town."
Susan McCabe, 42, a hospital worker from Northowram, Halifax, said: "I don't see a problem with the change. As it is the roads get very busy and this will mean they won't be as hectic as normal.
"It will help during winter when the roads get icy and if this helps slow traffic and reduce accidents I can't see a difficulty."