Real-world vehicle emissions of carbonyls compounds (CC) were determined at the Rebouças Tunnel, Rio de Janeiro (Brazil). The tunnel is a two-bore tunnel with three lanes in each direction and has a length of 2840 m, divided in two sections. On average, approximately 5,000 vehicles (95% light duty) were passing the tunnel per hour. Sixteen samples were simultaneously collected 500 and 1500 m inside from the ent...