Adelaide traffic reaches unacceptable levels | report

Traffic is slowing to a crawl as peak-period travel times on major roads blow out and Adelaide commuters spend up to an extra 50 hours a year in their cars.

As traffic volumes peak with the start of the school year today, the RAA says its annual survey of a dozen key routes shows flows are at "unacceptable levels" and that city streets are "not coping" with increasing volumes.

Roads with the greatest increases to travel times in the past 12 months were North East Rd, Goodwood Rd, Main North Rd, Marion Rd and South Rd.

The RAA says many roads are now at saturation point.

more needs to be done to improve capacity

The survey shows cars on 10 of the 12 roads failed to reach travel speeds of at least 30km/h, or 50 per cent of the speed limit, on average in the morning peak.

The situation in the afternoon peak was only slightly better, with cars on seven of the 12 roads failing to reach acceptable average speeds.

Drivers are spending more than 50 hours a year extra in traffic because they cannot travel at acceptable speeds during these peak periods, according to the RAA, which late last year also found that the cycling is quicker than driving in peak hour on some of the city's major commuter routes.

RAA spokesman Charles Mountain said its Metro Travel Time survey "once again" highlighted that many of Adelaide's roads were still not coping with increases in volumes.

"In particular, large sections of the inner-city ring route and main roads are struggling during peak periods, and more needs to be done to improve capacity," Mr Mountain said.

Mr Mountain said the survey highlighted the deficiencies of the city's Inner Ring Route, large sections of which are now at saturation point.

He said major roadworks such as underpasses or overpasses "should be considered" to alleviate the "pressure points" at the following junctions: Goodwood and Greenhill roads, Port Rd and Park Tce, Glen Osmond and Greenhill roads and Northcote and Robe terraces.

The capacity of Greenhill Rd could also increase with wider lanes, Mr Mountain said.

The major areas of congestion during the 2014 survey included:

SOUTH Rd, between Torrens Road and Port Road, which recorded an average speed of 7km/h during the morning peak period, taking an average of 12 minutes and 30 seconds to travel 1.6km.

BRIGHTON Rd and Anzac Highway during the morning peak period where the average speed was 9km/h.

GREENHILL Rd, between Goodwood Road and Anzac Highway with an average speed of 9km/h during the morning peak period.

HENLEY Beach Road, during the morning peak between Airport Road and Holbrooks Road, recorded an average speed of 10km/h.

MARION Rd, between Mooringe Avenue and Cross Road, which recorded an average speed of 11km/h during the afternoon peak period PAYNEHAM Rd, from Stephen Terrace to Fullarton Road recorded an average speed of 14km/h during the morning peak.

I used to drive along Main North Rd ten years ago...it was much better then

In some good news for motorists, average speeds on the northern section of South Rd, including the Superway, reached 36km/h.

Brighton Rd, although having some of the slowest sections across the city, in the past year recorded an increase in average speeds by 3km/h to 32km/h in morning peak and 5km/h to 32km/h in the afternoon peak.

Regular Main North Rd commuter Lisa Stuart said the amount of traffic had increased and time it took to clear intersections risen along her route from the outer northern suburbs to the city in the past decade.

"I used to drive along Main North Rd ten years ago before I moved to Sydney and it was much better then," the 28-year-old Elizabeth Downs resident said.

"The traffic is bad in Sydney but it does have freeways."

BIGGEST INCREASES TO TRAVEL TIMES IN THE PAST 12 MONTHS:

North East Rd (Modbury to city) extra 6 mins 25 secs (am peak)
Goodwood Rd (Pasadena to city) extra 4 mins 49 secs (pm peak)
Main North Rd (Pooraka to city) extra 3 mins 53 secs (am peak)
Marion Rd (Darlington to Henley Beach Rd) extra 3 mins 21 secs
South Rd (St Marys to Anzac Highway) extra 2 mins 58 secs