The stretch of road to receive the most attention will be between Burns Point and Rosehill Rd, where seven crashes have already been reported this year.
In March, Dunedin City Council staff were asked by councillors, concerned after a spate of crashes, to investigate the issue of cars going off Portobello Rd into the harbour.
Council senior traffic engineer Ron Minnema told councillors this week the number of crashes on the road had decreased in the past five years, especially on the sections of the road that had been widened as part of a programme to upgrade peninsula roads that started in 2008.
The number of crashes was expected to decrease further as the road was widened in more places.
There were 18 crashes on the section of Portobello Rd between Andersons Bay Rd and Harington Pt Rd last year, compared with 45 in 2007, he said.
Twelve crashes had been reported on the road so far this year.
The main contributor to the majority of crashes was driver error - motorists travelling too fast or inattentively.
That was supported by local policeman Senior Constable Lox Kellas, who told the council's infrastructure services committee on Tuesday that, in his experience, most of those who crashed into the harbour were locals and the main contributing factor was driver error.
On the worst section of the road - the 4.5km stretch between Burns Point and Rosehill Rd - 53 crashes were reported between 2007 and 2011, 47 of those in the section between just south of Weller St and Rosehill Rd.
The next-worst section was between Portsmouth Dr and Vauxhall (28 crashes), followed by the section between Rosehill Rd and Marion St East (26 crashes).
Mr Minnema said driver behaviour would continue to be monitored and would be targeted through a series of education campaigns, but a closer investigation of the common contributing factors to crashes at the same spots along Portobello Rd also revealed nine sites of concern with the road.
Staff now intended to take remedial action at those sites before the end of the 2012-13 year, before other planned road upgrades, he said.
The sites were the intersection of Portobello Rd, Portsmouth Dr and Shore St, six spots on the stretch of road between Burns Point and Rosehill Rd, one between North King George St and Bacon St and one near Grassy Point.
What measures would be taken at those spots was yet to be finalised but work could include re-marking road lines, new delineations, signage or resurfacing.
To put the crashes into context, there were 1300 in Dunedin every year, Mr Minnema said in his report to councillors.
Across the city, 46 sites had been prioritised for remedial action based on a formula involving the number of crashes and social costs of those crashes, but only one of those on Portobello Rd reached the threshold - at the intersection with Portsmouth Dr and Shore St.
That intersection needed further investigation into what measures would best improve it, Mr Minnema said.
Sections of the road between Ivanhoe Rd and Marion St and Luss Rd and King George St had been identified as two of 13 high-risk rural roads across the city.
Investigations into how to make those sites safer were ongoing.
Improvements at other, similar, sites included the installation of edge marker posts, reductions in speed limits and installation of guardrails.
