School fleets in the United States consume millions of gallons of fuel annually. Transportation costs make up for a large part of the expenditure and affect school budgets.
Fuel efficiency and fuel economy are, therefore, very important factors in the operation of school bus fleets. The testing of fuel economy is a complicated procedure and only effective testing methods can render accurate results.
However, fuel-efficient school buses share some important common features (in the body of the bus as well as external to it) and some of them are listed below.
1: Driver’s Behaviour
How a school bus driver steers the vehicle is the foremost factor to be considered when discussing fuel efficiency. The driving behaviour has an impact of almost 30 percent on the fuel efficiency of the vehicle.
Drivers who avoid sudden acceleration and excess idling have vehicles exhibiting higher fuel efficiency.
For every hour of idling of the engine, the fuel economy is known to reduce by almost 1 percent. Idling can be controlled with the help of technology.
Installing a vehicle idle shutdown timer on the bus will be helpful. This helps to reduce emissions and improve fuel efficiency by limiting the time that the engine remains in the idling mode.
Smooth acceleration by the drivers after ignition ensures that engine runs in the peak efficiency zone. If they operate the engine below optimum range levels, carbon build-up occurs and over time the fuel efficiency decreases.
Fuel efficiency is higher when the drivers do not hit the brakes regularly. It is important to coast whenever possible.
2: Condition of the tires
It’s a good idea to choose tires that are designed to have a longer life. This is because the normal buses are subjected to harsher bus-duty cycles.
The scrub loads of school buses tend to be higher on account of frequent starting and stopping of the bus. School buses should have tires designed to have a longer life, they should have a deeper tread.
Tires should have proper inflation. Under-inflated and over inflated tires can reduce fuel economy and lessen the lifespan of the tires
3: Synthetic Lubricants
Synthetic lubricants when used on the axle and transmission help to improve fuel economy by 1 percent. The axle lubricant when used extends drain interval.
Synthetic lubricants have a better flow at lower ambient temperatures than mineral oils and tend to be more efficient at these temperatures. However, care has to be taken not to exceed fill levels as this works to decrease fuel efficiency.
4: Axle Alignment
Improper alignment of the axle contributes to reduction of the fuel economy. Misalignment increases drag and tires get worn out faster. It also reduces fuel economy by 0.6 percent.
5: Proper Specifications
Fuel efficiency is heavily dependent on proper component specifications that have to be stated during the purchase of the buses. The school authorities seek the help of technical experts to specify and install the right components that would help to improve fuel efficiency.
• Selection of a fuel-efficient engine is the first step. Latest models are more fuel efficient than their pre-2007 counterparts.
• Use of the fuel economy mode in auto-transmission vehicles serves to improve fuel efficiency by up to 5 percent. Other features of auto transmission that can be used to improve fuel efficiency include the use of shift energy management/transmission retarders.
• The shift energy management systems combined with improved torque delivery in modern school fleets improve fuel efficiency. The rear axle ratio of such buses is lower and this maintains vehicle response.
6: Utilize Hybrid Electric Vehicles (HEVs)
Use of HEVs is a great way to improve fuel efficiency. These fleets provide substantial savings in fuel when compared to their non-electrical counterparts.
The fuel efficiency of HEVs is high and is improved by as much as 50 to 60 percent. The selected technology (plug-in and non-plug-in) also contributes to a small extent.
7: Convert to modern Diesel Engines
Diesel engines built in these times are cleaner than the engines built in the 1980s. Diesel is undoubtedly the most cost-effective fuel that can be used by the bus engines.
It provides better economy than other natural gas alternatives. Many of the older buses are retrofitted with the newer engines as retrofitting techniques have also improved over the years.
The modern yellow fuel efficient diesel-powered school fleets are more reliable, safe and durable; the diesel fuel provides 25 to 30 percent additional mileage which increases their fuel efficiency.