Subway and commuter train workers in Brazil’s biggest city went on strike yesterday, paralyzing a system used daily by more than 4 million people and exacerbating already heavy traffic jams.

Ciro Moraes, a spokesman for the transportation workers’ union, said about 8,000 of the city’s 9,000 subway workers had walked off the jobs on Wednesday to demand a salary increase of about 20 percent (what amounts to an increase of about 14.99 percent in real terms). The city’s transport authority, the São Paulo Metro Company, has offered a 7-percent raise, or 4.15 percent in real terms.

São Paulo’s metro has fives lines, one of which is run by a private operator and was not affected by the strike. Of the affected lines, the red line is the most active, transporting 1.5 million passengers daily.

Transit authorities estimate that about 730,000 people were affected. Commuters without cars walked or waited in long lines for public buses. Those with cars sat in heavy traffic—at the peak of traffic, 249 kilometers (155 miles) of roads were backed up, breaking the city’s previous record of 191 km (118 miles), set in November 2004 after heavy rains. Angry subway users protested against the strike by blocking roads, throwing rocks and deflating buses’ tires and were dispersed by police with tear gas and rubber bullets.

The paralysis of Brazil’s business capital by a single, previously announced workers’ strike is in part a reflection of Brazil’s failure to invest in upgrading and developing new infrastructure. While other emerging economies like China and India also experience infuriating traffic in major metropolitan areas, Brazil’s investment in infrastructure—only 17 percent of GDP in recent years—has lagged behind theirs (44 percent of GDP in China and 38 percent in India). Economists say that poor infrastructure is one major factor—along with high taxes and cost of labor—limiting Brazil’s economic competitiveness.

Transportation systems in other major Brazilian cities, including Natal, Recife, Belo Horizonte, and Salvador, experienced similar logjams Wednesday in a separate strike by subway workers, bus drivers and commuter train operators.