* Merkel's conservatives vow to end traffic jams, burglaries
* NRW is Germany's most populous state and bellwether region
* A CDU victory in NRW will be major setback for SPD
By Joseph Nasr
BERLIN, May 14 (Reuters) - German Chancellor Angela Merkel's conservatives are hoping to unseat the ruling Social Democrats (SPD) in an election on Sunday in the country's most populous state, the final electoral test for both parties before a federal vote in September.
The Christian Democrats (CDU) want to seize upon anger among the 18 million inhabitants in North Rhine-Westphalia (NRW) over clogged traffic, rising crime, an underperforming education system and relatively high unemployment to win.
The SPD has ruled NRW for most of the post-war years and losing power in what they regard as their bastion would raise serious doubts about their chances of unseating Merkel in just over four months.
With 32 percent, the CDU are one percentage point ahead of the SPD in the state and they have a better chance than their rivals of forming a coalition after the vote with their resurgent traditional partners, the liberal Free Democrats.
It would be the third state election victory this year for the conservatives, who have retained power in Saarland and unseated the SPD in the northern state of Schleswig-Holstein.
They have also extended their lead over the SPD at the national level.
Support for the SPD surged in January when the party appointed former European Parliament president Martin Schulz as its leader, vowing to reverse unpopular labour market reforms that expanded the low-pay sector and boost welfare.
But his message of social justice has lost its appeal among voters as he has yet to spell out details of his plans and how much they would cost. The SPD is trailing Merkel's CDU and its Bavaria-based Christian Social Union sister party by about 10 percentage points at the national level.
In NRW, CDU candidate Armin Laschet has attacked SPD State Premier Hannelore Kraft for failing to tame a rise in crime and fix the state's crumbling roads, frustrating Germans who like to drive on the state's extensive Autobahn network where long stretches have no speed limit.
Some 30 percent of all traffic jams reported in Germany last year were in NRW. In addition, 38 percent of all burglaries took place in NRW, home to 22 percent of Germany's population.
"I think this is disproportionate and the state government must do something about it, because it is responsible for that," Merkel said earlier this week of the rise in crime in NRW.
"The numbers speak for themselves and Armin Laschet is totally right that something must be done."
The conservatives are running on a platform of beefing up security - raising prison terms for offenders and providing more funds for the police and security forces.
"Being stuck in traffic is time from people's lives," Merkel said. "When you add all the time up over a year, it has become a huge amount of time for commuters in NRW."
SPD candidate Kraft hit back at Merkel, saying she was ignoring the SPD's achievements on security in NRW. The SPD aims to increase the number of new police recruits each year to 2,300 from 1,100 in 2010, Kraft said, in a state with more cities than other regions, which makes it more vulnerable to crime.
"She is an unworthy chancellor," Kraft told the broadcaster WDR in response to Merkel's criticism.
Kraft has ruled NRW since 2010 in a coalition with the environmentalists Greens, whose support among voters has more than halved to just over 6 percent, making it difficult for the SPD to muster a coalition, especially as their natural partners, the hard-left Die Linke, are also on 6 percent.
"It's going to be a unique election battle," said Merkel.
Reporting by Joseph Nasr; Editing by Ros Russell