India though one of the largest market for buses in the world, never had a large fleet of sophisticated city buses. Indian cities are growing and population was getting concentrated in the cities, but the city bus services were never upgraded. The first major change we saw, was in 2005, with the launch of semi low floor buses. These buses had a two step entry and had an entry height of 900mm. This 900mm platform was spearheaded by Ashok Leyland with Viking SLF buses.
In 2006 Volvo launched B7R LE a low entry 400mm floor height city bus in Bangalore. This was a radical change in the way people travelled in cities. But the Volvo bus population was limited only to few hundred buses that too only in Bangalore.
It was only during 2008, when Delhi Transport Corporation decided to upgrade its fleet by introducing 400mm entry height buses we got introduced to low entry buses in mass numbers. The decision was taken on account of Common wealth games. Its to be noted that it was DTC, though was always been criticised for running lesser and poorly maintained fleet set the trend of procuring step less entry or 400mm entry height buses in large number. The technical requirements was the base for Urban Bus Specification which was formulated in the later stage. The tender requirements was so strict that both Ashok Leyland and Tata Motors never made buses to meet those specs before. They worked day and night for moths together to deliver the buses they got allotted.
But there are two ways of making a 400mm entry buses. We try explaining them here in this post.
Low Entry Bus:
These are regular rear engine buses, in which engine, cooling systems and drive line are located conventionally – the engine is located in the centre (in the rear portion), cooling system in the side and drive line from the engine travels to regular axle. This is how rear engine buses was developed and they continue to be the same way. This kind of packaging occupies more space in the Rear Over Hang (ROH). The primary disadvantage of this type of vehicle integration is, we will have a step in the chassis from the start of rear axle and moves upwards.
Due to raised floor in the rear over hang, number of standee passengers is limited and is preferred in the wheel base area only. Also we could have a step less door entry only in the Wheel Base and Front Over Hang of bus. So is the reason they are called only Low Entry(LE) – they are low only in the entry point.
- Cost and complexity of these buses are comparatively less.
- Conventional vehicle integration and hence mechanically less complex.
- 400mm (max)
- Airport transfers
Low Floor Bus:
The difference between this and regular rear engine low floor buses lies in the packaging of power train and cooling systems. In these buses engine normally offset mounted (towards one side of the rear portion), and cooling systems are remote mounted either above the engine towards roof or mounted towards the other side of the chassis. Since the differential is offset from the centre (inline with the engine) the axles used in this type are portal axles.
This means the drive line is completely offset with respect to the centre line of the bus. This type of vehicle integration frees up lot of space from the rear axle while we move backwards. Due to this design, in general the rear overhang of these buses can be lesser in comparison to low floor buses. As a result, we can have flat floor from front to rear. This makes these buses to have low entry door at Front Oveg Hang (FOH), Wheel Base (WB) and also at Rear Over Hang (ROH).
- Possibility of having multiple locations of low entry passenger door.
- Pax capacity of these buses can be upto 10% higher as they can accommodate more standee passengers.
- Quite expensive and complicated design.
- Technically complex and hence the maintenance as well.
- 400mm (max)
- Airport transfers
Columbus Low Floor Bus saloon – showcased in Bus World 2016, Bengaluru
We don’t have any of these buses commercially produced in India, but we saw some of the concepts like Starbus Hybrid, Columbus in major auto shows.
Tata Starbus Hybrid – Showcased in Auto Expo 2016