The works on Gdynia Way near Plymouth's city centre have been in place since June to widen the road to three lanes.
But police said they had seen an increase in the number of collisions on the Maxwell Road, Macadam Road junction.
Plymouth City Council (PCC) said a new set of temporary traffic lights would be put on the junction.
Pc Ian Tanner, Plymouth's road casualty reduction officer said: "There have been some collisions since the new system was put in place, with four or five injury collisions in that area.
"The council are diverting quite large volumes of traffic on to roads that, although perfectly up to the job, people don't usually travel on, and as a result it hasn't worked as well as we would have liked it to.
"It's a balancing act for the council, as to what is the best thing to do, to keep the traffic moving as well as they can and to keep the level of injuries down."
Pc Tanner added that the increase in collisions could also be a result of drivers, familiar with the route, not reading new signs properly.
In a statement, PCC said: "During the last couple of months it has become apparent that there could be further improvements to the revised junction layout.
"The decision to install temporary lights has been made after routine discussions with various stakeholders including the police.
"The lights will reinforce the changed priorities and help drivers negotiate this junction."
The council said that up to 1,000 drivers used the junction each hour.
The new traffic lights will give priority to traffic travelling between Plymstock and the city centre in the morning and vice versa in the evening, until the work is completed in October.

Mark Turner, 55, tried to use an EpiPen to counter the severe allergic reaction but spilled the contents, a hearing at Exeter's County Hall was told.
His wife then successfully used another pen to administer an injection, but he died from the reaction to the sting at his home on Dartmoor, Devon.
A coroner recorded a conclusion of accidental death.
More on this story plus more Devon and Cornwall news
Mr Turner kept three hives near his home as a hobby and to make honey.
He had previously been diagnosed with an allergy to bee stings, but tests had found the severity of his condition was on the "lower end".
His wife Ali said on the day of his death in November 2015 the father of three ran into the house and then collapsed on the floor gasping for breath.
He got out of the protective suit and grabbed the EpiPen but it misfired and the contents ended up on the floor.
Mrs Turner then got a second pen and injected his leg.
She said: "He was still conscious but delirious. He was grey and pale and his breath was shallow. He was not responding."
He died about 20 minutes later despite the efforts of paramedics.
A post-mortem examination concluded Mr Turner died from the anaphylactic allergic reaction caused by the sting to his neck.
His wife said he had gone to see his GP in May 2015 and was given antihistamines and Epinephrine injections after suffering a reaction.
Mrs Turner said her husband was "fit and healthy" and said had he known there was a risk of dying "he would have given up the bees".
Assistant coroner Luisa Nicholson said both EpiPens had been tested and did not have any defects.
The number of road traffic collisions in a Devon city has increased following the introduction of major roadworks.
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An amateur beekeeper died after he was stung on the neck inside his protective suit, an inquest has heard.