that low floor trams have 15% higher maintenance costs for the rolling stock, and 20% higher maintenance costs for the infrastructure on average. Among the problems observed is that the missing bogies result in a higher level of wear and tear. Many low floor trams have fixed bogies which increase track wear and tear, while decreasing the speed at which a tram can drive through a curve (usually 4–15 km/h in 20 m radius curve). The Škoda ForCity and the newest Alstom Citadis X04 try to counter the effect with low floor pivoting bogies while maintaining 100% low floor design. Prior to the new design, pivoting bogies could only be used under high floors, hence such trams could only be part low-floor, with high-floor sections over the pivoting bogies. Historic examples The idea of a low-floor tram dates back to the early 20th century when a number of trolley systems began experimenting with various "stepless" designs. Perhaps the most notable is the Hedley-Doyle Stepless car introduced in 1912 for use on Broadway in Manhattan. A number of other cities also purchased Hedley-Doyle Stepless trams after seeing their success in Manhattan. Since these cars had a unique appearance compared to any other trams running at the time, they earned a number of nicknames, including hobble skirt cars, public welfare cars, and sow bellies. Typical floor heights To put things into perspective, here are some typical floor heights for public transport vehicles, old and new: Ultra Low Floor tram — 180 mm (7 inches) Low-floor tram — 300 mm to 350 mm (11.8 to 13.78 inches) High-floor tram — more than 600 mm (23.62 inches) Heavy rail rapid transit — 800 mm (31.5 inches) to 1200 mm (47.25 inches) North American inter-city rail passenger cars — 1350 mm (51 inches) List of low-floor trams by country manufactured and manufacturers Belarus Belkommunmash AKSM-743 - Third Generation tram on Minsk tramway AKSM-843 - Fourth generation tram on Minsk tramway Canada Bombardier Transportation (are subtypes and more) A32 Flexity Swift Citytram Cobra CR4000 Flexity Swift GT8-100D/2S-M ET 2010 Flexity Swift (Tram-train) E-class Melbourne tram Flexity Swift Flexity 2 Flexity 2 (version for Blackpool) Flexity Berlin (Incentro family) Flexity Classic Flexity Freedom Flexity Link Flexity Outlook Eurotram Flexity Outlook Cityrunner Flexity Outlook Olympic Line Flexity Outlook (version for Toronto) GT8-100D/2S-M HF6 Flexity Swift (not low-floor, but due to the high platform is wheelchair-accessible) Incentro Incentro AT6/5