Vehicle reinforcement for hollow structural member, having decreasing-thickness end portions

A hollow structural member (10, 160, 192, 194, 196, 198, 244, 248, 286) including a hollow body portion (12, 192a, 192b, 194a, 194b, 196a, 196b, 198a, 198b, 224, 248, 286a, 286b), and a reinforcement (16, 40, 60, 80, 110, 120, 130, 140, 150, 162, 208, 220, 228, 238, 252, 272, 292, 294) having a hollow structure fixedly disposed within the body portion in close contact with the inner surface of the hollow body portion. The reinforcement includes a thick-walled portion (18, 42, 62, 82, 96, 102, 164, 112, 122, 132, 142, 152, 204, 216, 234, 256, 276, 294) as a longitudinal central portion thereof, and two decreasing-thickness portions (20, 44, 66, 98, 104, 166, 114, 124, 134, 146, 154, 206, 218, 236, 258, 278, 296) as longitudinally opposite end portions. Each decreasing- thickness portion has a wall thickness which continuously decreases in a longitudinal direction from the thick-walled portion toward the longitudinal end of the corresponding end portion of the reinforcement, such that the wall thickness at the longitudinal end is substantially zero.