After making a number of design changes, unibus U4-220-T2 has been put for type testing. During the modernisation, which took place in 2022–2023, engineers focused on improving the customer qualities and reliability of the unibus systems.
The key improvement was the introduction of pneumatic elements in two stages into the suspension of unibus U4-220-T2. This significantly improved the running smoothness and reduced vibration and noise levels. New compressors, variable capacity fans were also installed. Completely new climate control units and air ducts have been developed to supply cold or warm air to the passenger compartment.
Leading Design Engineer of UST Inc. Dmitry Vikhrienko said that all tests were carried out at speeds of up to 50 km/h and the preset parameters were fully confirmed.
Smooth run at the level of a business class car
The test results showed that the 48-seater unibus U4-220-T2 is smoother than underground cars and trains. The evaluation was carried out on a scale of 1 to 5, the lower the number — the better. Thus, the train cars have a running smoothness of up to 3.0, underground cars — up to 3.25, and unibus U4-220-T2 — not more than 2.5.
Dmitry Vikhrienko noted that the running smoothness of this unibus is at the level of a business class car.
Noise level is 10 times less
The external noise level of unibus U4-220-T2 according to the test results — 75.5 dBA, and the internal noise level, depending on the measurement point, — from 76 to 78 dBA.
If compared to other urban rail transport such as tram and underground, the external noise level of an underground train when travelling in a tunnel is between 90 and 100 dBA, the internal noise level reaches 95 dBA. Noise at stations during train acceleration and braking — 80 dBA.
External noise of the tram when travelling on the tracks on crushed stone backfill at 60 km/h is 86 dBA. If there is an asphalt surface between the rails, the noise reaches 91 dBA. Inside the tram, noise — 83 to 84 dBA at 45 km/h.
Testing of unibus U4-220-T2 will end in November-December this year. As noted by the Head of the Field Testing Bureau of UST Inc. Alexander Loktevich, during the research, a noticeable improvement in comfort parameters was recorded. He also emphasised that analytical work is being carried out and the tests are ongoing.