More than 150 objections have been lodged over plans to redevelop Thirroul Plaza into a bigger shopping centre with three-storey apartment buildings.

The vast majority share an opposition to the number of apartments, because of the impact on congested Lawrence Hargrave Drive, a mostly single-lane road which becomes clogged on a regular basis.

The traffic study commissioned by the developer concluded 82 new apartments in the middle of Thirroul would produce just 33 vehicle movements in the morning peak, and 24 on the afternoon peak.

Read more: Developer says traffic impact overstated, residents say it would devastate the heart of Thirroul

Some say this is unrealistic. Lifelong Thirroul resident John Nicholls said the traffic study, conducted on September 19-21, 2019, didn't properly represent the reality.

"I've lived in Thirroul all my life so I know what it's become," he said.

"It's not a typical period when you've got 100mm of rain on those days when the survey was done.

"It probably sells the problem short in terms of how much time the traffic is a problem in Thirroul."

Thirroul Plaza Pty Ltd spokeswoman Emma Foster defended the consultants' report.

"The Traffic Impact Assessment was conducted by independent third-party consultants, if you refer to the appendix of the report compiled and available with the DA you can see they analysed traffic data from 6.15am-10am, not just the peak hours," she said.

In fact, the most affected intersection, King St and Lawrence Hargrave, was modelled only from 8-9am.

"Surveyed peak hours [at that intersection] are therefore as follows: AM peak: 8am-9am. PM peak: 3pm-4pm. Saturday peak: 12.45-1.45pm," the traffic study states.

The modelling states each two-bedroom apartment would create just 0.42 vehicle movements in the morning peak, and 0.3 movements in the afternoon peak. The proposed shopping centre would create 531 trips each peak, and 704 on Saturday.

This is when using the "high density" metric from Roads and Maritime Services to calculate additional traffic flow from apartments.

High density is applied to buildings with more than 20 apartments and usually more than five storeys high. None of the proposed Thirroul Plaza buildings are of that size, but their combined scale is well past the 20 apartments threshold.

High density modelling assumes less car ownership as people are more likely to be living in inner-city areas near public transport options. But in car commuter-heavy suburbs such as Thirroul and much of Wollongong, there are questions as to whether the modelled traffic is realistic.

The owners behind the development proposal are Austinmer engineer Angelo Forte, of Mainland Civil, and his partners, and Austinmer builder Mark Forte, of Genesis construction company.

Ms Foster said the proposal actually produced less traffic than other plans which could be allowed on the site.

"The residential component of the development has the least impact on traffic movements than any other use of the allowed building area," she said.

"The 82 units only contribute 6 per cent of the whole of the traffic generation for the development.

"The site is zoned to allow approx 15,000 square metres of retail to be built, if the owners did that and didn't include residential, the independent traffic consultant calculated there would be over 1000 vehicle movements in the morning and afternoon peaks.

"The previous approved DA for the site had a retail area of 5900 square metres which would of generated over 700 car movements at each peak period. The new owners who live locally did not want to do that to the area and therefore the current proposal which includes the residential apartments and only 4,300 square metres of retail, is believed to be a good balance between uses."