The main feature of the Toyano Traffic Park is the go-kart track, where you can drive a pretty speedy kart for 100 yen (150 yen if you are accompanying a child). You can buy tickets for the karts from a machine on the bridge above the track, then just go down the stairs to where the karts are lined up.
After a trip around the course, there's a small park with swings and slides, as well as coin-operated cars for very young children. If you follow the track under the overpass, you can see a few peacocks, and beyond that is an area where people practice horseback riding.
Finally, there is a decommissioned city bus and two fire engines where kids can sit and push all the buttons and switches.
Toyano Traffic Park website: http://kosya-niigatacity.jp/green/facility/49/
