Euthanasia programme. Under Action T4, the Kalmenhof served as a way station for Hadamar killing centre. After the gassings at Hadamar came to an end in the face of public protests, especially from the churches, the Kalmenhof itself, in the course of Aktion Brandt, became a killing institute; patients here were murdered with poison injections. Shortly after the war, reports of young wards being mishandled came to light. Eleven formerly independent villages were merged as of 1971 into Idstein, under the framework of municipal reform. Population development (as of 31 December) Politics Coat of arms The town's arms might be described thus: Azure a round castle wall embattled with two portcullises open, the wall enclosing two towers, the whole Or, with peaked roofs gules, between the portcullises an inescutcheon azure with a lion rampant Or armed and langued gules among six billets Or. The inescutcheon is the arms borne by the House of Nassau. The town's flag also bears this design set against orange and blue, Nassau's colours. Twin towns – sister cities Idstein is twinned with: Heusden, Netherlands Lana, Italy Şile, Turkey Uglich, Russia Zwijndrecht, Belgium Economy and infrastructure Transport Idstein has an interchange on the Autobahn A 3 north of Wiesbaden between Niedernhausen and Bad Camberg, and a railway station with direct connections to Limburg an der Lahn, Frankfurt am Main and Wiesbaden. The building of a bypass, Bundesstraße 275, lessened the traffic in the historic Old Town. However, the traffic volume in the town core is still very high. At intersections in the town core, roundabouts have improved the traffic flow, in some places noticeably. The Südtangente (south "tangent" road), which had been planned since 1981, was completed in 2009, reducing traffic in town further. It links two new development areas. Of the €9,000,000 for the project, roughly 60% was borne by the state of Hesse. Local transport Within Idstein town limits are two railway stations on the Main-Lahn Railway (Main-Lahn-Bahn), Idstein and Wörsdorf. There are hourly trains serving the Frankfurt/Wiesbaden–Niedernhausen–Limburg run into the evening. In Niedernhausen there is also a transfer point with S-Bahn line S2 towards Dietzenbach through the Frankfurt and Offenbach S-Bahn tunnels. The Idstein town bus (de Idstaaner) serves 3 lines: 221 Railway station–Eisenbach–Taubenberg–Gänsberg–ZOB Schulgasse–Railway station (formerly 401) 222 Railway station–ZOB Schulgasse–Gänsberg–Taubenberg–Eisenbach–Railway station (formerly 402) 223 (booster line) Railway station–Dasbach–Heftrich–Niederrod (formerly 403) The town bus is run by ORN (Omnibusverkehr Rhein-Nahe). It uses