Autonomous Rail Rapid Transit

Autonomous Rail Rapid Transit (ART) is a lidar (light detection and ranging) guided articulated bus system for urban passenger transport. Developed and manufactured by CRRC through CRRC Zhuzhou Institute Co Ltd, it was unveiled in Zhuzhou in the Hunan province on June 2, 2017. ART is specifically referred to as a train or rapid transit by its manufacturer, however the public describes it as a bus. Its exterior is composed of individual fixed sections joined by articulated gangways, resembling a rubber-tyred tram.

The system is labelled as "autonomous" in English, however, the models in operation are optically guided and feature a driver on board. Despite "rail" in the name, the system does not use rails.

Automated Rapid Transit systems (ARTs) can operate independently without the need for a guiding sensor and as a result, they fall under the classification of buses. Consequently, vehicles deployed on these routes are mandated to display license plates.

Background
Before the announcement by CRRC, optical guided buses have been in use in a number of cities in Europe and North America, including in Rouen as part of Transport Est-Ouest Rouennais, in Las Vegas as a segment of Metropolitan Area Express BRT service (now discontinued), and in Castellón de la Plana as Line 1 (TRAM de Castellón). The guidance system technology used on these systems was called Visée under their original developer Matra, and is now named Optiguide after being acquired by Siemens.

Description
An ART vehicle with three carriages is approximately 30 m long. It can travel at a speed of 70 km/h and can carry up to 300 passengers. A five-carriage ART vehicle provides space for 500 passengers. A four carriage model was introduced in 2021 which can carry 400 passengers. Two vehicles can closely follow each other without being mechanically connected, similarly to multiple unit train control. The entire ART has a low-floor design from a space frame with bolted-on panels to support the weight of passengers. It is built as a bi-directional vehicle, with driver's cabs at either end, allowing it to travel in either direction at full speed.

The 6.5 km long ART lane was built through downtown Zhuzhou and inaugurated in 2018.

Sensors and batteries
The ART is equipped with various optical and other types of sensors to allow the vehicle to automatically follow a route defined by a virtual track of markings on the roadway. A steering wheel also allows the driver to manually guide the vehicle, including around detours. A Lane Departure Warning System helps to keep the vehicle in its lane and automatically warns, if it drifts away from the lane. A Collision Warning System supports the driver on keeping a safe distance with other vehicles on the road and if the proximity reduces below a given level, it alerts the driver by a warning sign. The Route Change Authorization is a navigation device, which analyzes the traffic conditions on the chosen route and can recommend a detour to avoid traffic congestion. The Electronic Rearview Mirrors work with remotely adjustable cameras and provide a clearer view than conventional mirrors, including an auto dimming device to reduce the glare.

The ART is powered by lithium–titanate batteries and can travel a distance of 40 km per full charge. The batteries can be recharged via current collectors at stations. The recharging time for a 3 to 5 km trip is 30 seconds and for a 25 km trip, 10 minutes.

Benefits and limitations
A 2018 article by a sustainability academic argued trackless trams could replace both light-rail and bus rapid transit due to low cost, quick installation and low emissions. Others have disputed the claims about cost and quick installations, and argued that ART is a proprietary technology with little deployment worldwide. Other experts have argued the technology is overhyped, that optical guidance technology is not new, and that current proposals largely represent a repackaging of the bus as a rail-replacement technology. As of 2022 there are no systems outside of China and few proposals. That may be because:
 * The system is not fully autonomous
 * The system is not rail-based and so has the ride qualities of a bus
 * The vehicles can get stuck in road traffic when not operated in dedicated rights of way
 * The required vehicles cannot be bought through competitive tender

Proponents have argued the lack of rails means cheaper construction costs. Multi-axle hydraulic steering technology and bogie-like wheel arrangement could allow lower swept path in turns, thus requiring less side clearance. The minimum turning radius of 15 m is similar to buses.



However, because the ART is a guided system, ruts and depressions could be worn into the road by the alignment of the large number of wheels, so reinforcement of the roadway to prevent those problems may be as disruptive as the installation of rails in a light rail system. Researchers in 2021 found evidence of significant road wear due to trackless tram vehicles, which undermined claims of quick construction, with the researchers finding significant road strengthening was required by the technology. The suitability of the system for winter climates with ice and snow has not yet been proven. The higher rolling resistance of rubber tires requires more energy for propulsion than the steel wheels of a light rail vehicle.

A few abandoned proposals for light-rail lines have been revived as ART proposals because of the lower projected costs. However, a different report, by the Australian Railways Association, which supports light rail, said there were reliability questions with ART installations, implying the initial suggested capital cost savings were illusory. A November 2020 proposal for a trackless tram system in the City of Wyndham, near Melbourne, posited a cost of $AU23.53M per km for roadworks, vehicles, recharge point and depots. Recently completed light rail systems in Australia have had costs of between $AU80M and $AU150M per km.

The Government of New South Wales considered the system as an alternative to light rail for a line to connect Sydney Olympic Park to Parramatta. However, concerns were raised that there was only one supplier of the technology, and that the development of "long articulated buses" was "too much in its preliminary phase" to meet the project deadlines. Instead, the plan was to build a light-rail line which would connect to another light-rail route already under construction, so passengers would not have to change vehicles.

The Auckland Light Rail Group, in its studies of trackless trams for the City Centre to Māngere line, found that trackless trams would have a lower capacity than claimed. The official specifications for the ARRT assume a standing density of eight passengers per square meter, whereas many transit systems have more typical standing densities of four passengers per square meter. Based on that, the 32 m long ARRT would more realistically have a capacity of 170 passengers, rather than the claimed 307. This would be only a slight increase over the typical capacity of conventional bi-articulated buses at the same passenger density (~150 passengers), and less than a typical 33 m long LRV (~210-225 passengers).

Proposed systems
Proposals, including vehicle testing, have been made in several countries.
 * China, Changsha. Changsha Meixi Lake to Changsha Municipal Government line, reported to start construction in 2021 for completion in 2022
 * China, Harbin. In May 2021 testing of a vehicle was underway with plans for an 18.2 km route with 11 stations. There are reports that stations have been constructed in January 2021 and trial operations will commence in August 2021.
 * China, Tongli. testing was underway with the service expected to open to passengers by the end of 2021.
 * China, Xi'an. Two routes. One with 18 stations over 29.7 km and second with 9 stations over 10.6 km.
 * Malaysia. Iskandar Malaysia Bus Rapid Transit in Johor. ART is one technology under consideration for the corridor. A three-month test of an ART vehicle, along with eight other bus types, began in April 2021.  In May 2024, the planned three line IMBRT was shelved due to unable to handle the traffic flow and affect the efficiency of the service. The traffic flow condition were projected to be much worse when the now under-construction RTS Link train line were expected to be completed by end 2026. The Johor government then propose the construction of Elevated Autonomous Rapid Transit (E-ART) system, a hybrid system utilising LRT infrastructure (without the LRT track) and ART system to replaced the now cancelled IMBRT.
 * Malaysia. Kuching Urban Transportation System in Kuching. The three line Kuching LRT project was proposed as a light-rail in 2018, but shelved due to costs. In 2019, the government of Sarawak announced that the ART technology had been selected instead, due to its lower costs for similar levels of service., the project has commenced construction and is under testing.
 * Mexico. Metrorrey Line 5 in Monterrey. This new line of the Metrorrey system is currently being built by the government of the state of Nuevo León. The public tender was awarded in 2022 to a consortium formed by the Portuguese firm Mota-Engil and the Chinese CRRC. On October 2023 Governor Samuel García presented the ART vehicles that would be used for the Line 5. It is expected to open on 2027.
 * Qatar. The system was considered for use during the 2022 FIFA World Cup, but was not pursued. In July 2019 a two-week test with one vehicle was undertaken in Doha, the first trial outside China.
 * Australia. In March 2021, the Australian Government provided $2 million to produce a business case to investigate a trackless tram on Scarborough Beach Road between the Stirling City Centre and the Perth CBD. In September 2023, a trackless tram was delivered to the City of Stirling to begin trials for a proposed route between Glendalough railway station and Scarborough Beach.