When railway vehicles run at exit transition curve, track twist produce wheel load variation. Especially if vehicle has air suspension, behavior of leveling valve increases diagonal differential pressure (Twist component of unbalance of air suspension pressure). Increase of wheel load variation makes margin of tight curve passing safety small. In order to improve running safety, reducing wheel load variation is very important. In this paper, authors have developed newly secondary suspension "connecting of front and rear air springs" for reducing wheel load variation in transition curve. This valve system can flow small amount of air at low differential pressure and flow large amount of air at high differential pressure. The developed air suspension system has evaluated with trial running in the test line. The test data show diagonal differential pressure is improved proximately 40%.
