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Azure Dynamics and Collins Bus Partner for Hybrid Electric Type A School Buses

The Azure Balance hybrid architecture. System shown is representative of strip van and cutaway vehicle. The Electric Power Assist System (EPAS) is located behind the tailpipe on the shuttle bus chassis. Click to enlarge.

Azure Dynamics Corporation has entered an exclusive agreement with Collins Bus Corporation of South Hutchinson, Kansas, the largest manufacturer of small school buses in North America .The new partnership will allow Collins to offer Azure’s proprietary Balance Hybrid Electric drivetrain as an option on Type A school buses built on Ford’s E-450 chassis. Type A school buses can typically transport between 14 and 30 passengers.

Working in collaboration with Ford Motor Company, Azure Dynamics developed the Balance parallel hybrid electric drive system for Ford’s E-450 Cutaway and Strip Chassis. The system combines a 100 kW AC induction traction motor, power electronics and 288 V NiMH battery pack with the conventional 5.4-liter Triton gasoline engine and 5-speed automatic Torqshift transmission.

A Collins bus. Click to enlarge.

The Balance hybrid can deliver up to a 40% increase in fuel economy, 30% reduction in greenhouse gas emissions and 30% reduction in maintenance costs.

The Balance system features:

  • Engine stop/start capability
  • Regenerative braking
  • Electric-only mode at low speeds
  • Electric launch-assist

School buses typically have frequent starts and stops and significant idle time picking up and dropping off children and while waiting in the queue. The Azure technology can help to significantly reduce fuel usage and emissions under these conditions.

Collins sells buses under both the Collins and Mid Bus brands in the United States and as Corbeil in Canada. The company has a developed network of distributors that serve its key markets and customers.

The Azure technology mated to the Ford E-450 chassis has undergone significant durability testing to be eligible for school bus programs. Azure technology is currently operating in major vehicle fleets in both the United States and Canada.



Azure bought the Solectria technology and has been doing good things with it. I like seeing more advanced school buses and RTD vehicles. Lots of stop and go without the black smoke coming out the back.


5.4L V8!!! Isn't this a bit much.
The 450 use to be available with 4.2L V6.


A good example of using technology where it can do the most good.

Kit P

“without the black smoke coming out the back”

Where I live, we maintain the school buses in good running order. I thought they would have figured that out in California sjc.


I try to not reply to people making snide remarks.

On the other hand, the Chevy Tahoe hybrid uses a 6L, larger than any other engine offered in that line of vehicles...seems a bit odd.

Andrey Levin


Chevy Tahoe uses cylinder deactivation. In essence, at light load, like at highway cruise on plain terrain, it uses only 4 cylinders out of 8, or 3 liters of displacement. It results in 10-12% additional fuel savings. V8 is minimal amount of cylinders which allows cylinder deactivation without significant increase in vibration, especially torsional vibration. In such behemots V8 with cylinder deactivation is probably better than smaller V6 without.


The larger gas triton ICE may actually give you better fuel economy since its much lighter than a diesel.. but I doubt it, maybe it was selected for cost reasons?..

Could also be emission problems with a start-stop diesel engine on a cold morning.

The early morning roar of a school bus will not be missed.. apparently they dont put mufflers on them!


dursun: The standard engine on the E-450 is the 5.4L now, and the only other options are the 6.8 V10 (gas) and the 6.4L V8 diesel (at vastly higher cost). The smallest engine available in any E-series van now is the 4.6L V8, and that's only in the lighter duty versions. All of the gas engines are the old two valve per cylinder design, not what they use in the F-series now, because the three-valve heads will not fit in the E-series. There has not been a V6 option in several years, and even when it was available, I believe it was only available up to the E-250. Keep in mind that the curb weight of an E-150 cargo van is ~6000 pounds, with a gross weight capacity of ~8600 lb. (and towing capacity well beyond that). As you move up to something like the E-450, you've gone up three categories of payload capacity. The standard weight rating of the E-450 (vehicle and payload combined) is 14,050 lb. To carry all that, the frame is heavier, the axles are heavier, the springs are heavier, etc. Regardless, Azure and Collins Bus don't get a choice from Ford to buy a smaller engine.

With the electronic throttle control they use there may not be much efficiency loss by using the 5.4 versus a smaller gas engine. The requirement to have secondary fuel enrichment under heavy load and high RPM ruins the fuel efficiency of almost any gasoline engine under those conditions (as far as I know the 2010 Prius is the first to completely avoid the need for enrichment). On the other hand, gasoline engines achieve their best fuel efficiency (for unit of work done) when the throttle is open fairly wide, but engine RPM is low. This reduces pumping losses but avoids secondary fuel enrichment. The trade-off is that it takes more fuel to run the large engine when load is light and even a smaller engine could handle it.

So if you compare a small gasoline engine in this application, where the driver has their foot on the floor a lot of the time, versus a bigger engine with electronic throttle that coordinates with transmission gear selection, you can come out ahead with the bigger engine. The computer will keep in a higher gear and open the throttle wide before ever considering downshifting, where in the same conditions with a smaller engine the throttle would be open wide, the engine RPM would be high, and excess fuel from secondary enrichment would be pouring into the intake. And in a hybrid application, the engine will be off during light-load conditions anyway.


Back during the years when Twit P. thinks I was in grammar school, I worked a project for Ford where we were working with a bone-stock 5l V8 powerplant with an experimental transmission.  One of our big problems was the stock engine map; we would have loved to have run right up at WOT in the lugging regime, but the stock map had considerable enrichment in those zones and both BSFC and emissions would have suffered.  Alas, due to the chimney organization of the company we didn't have any way to get a more suitable engine map.

Andrey Levin


With inclusion of SFTP US06 test procedure (aggressive driving and hard acceleration) in emission tests, EPA forced car manufacturers to practically eliminate WOT fuel enrichment.


I may be sastisfying to read that Collins and Ford are experimenting with hybrid drivetrains, but for these uses the vehicle should be low-floor. Their entire frame should be redesigned along with adding the hybrid drivetrain.

The high-floor para-transit van is particularly inconvenient for seniors and disabled. Easy boarding is just as important for school children. High-floor lifts are complicated, slow, and prone to break down. Low-floor ramps are a simple hinged floor that can be bypassed manually.

I've seen professional conversions of rear-wheel drive Ford vans to low-floor. It's possible. Lowering center-of-gravity should improve handling and stability to make the vehicles safer. Now's the time to demand more from auto manufacturers.


I understand that you have to crawl before you can walk, but I hope no one at Ford or Collins is fooling themselves with this marketing exercise. The Mercedes Citaro hybrid is an 18 meters long articulated bus powered by a 4.8L diesel.
I'm overseas right now and everywhere I see these 20 passenger minibuses powered by 3.2L engines.


Hybridization is a plus for school buses. A 5+L, V-8 ICE seems to be an overkill. With a 100 KW e-motor, frequent stops and very light load most of the time, a much smaller 3L ICE should be more than enough. A second battery pack could be a worthwhile addition.

We lived (for a very short time) a few blocks away from a country regional school and the 30+ noisy school buses were too much for us. We had to go to Florida for 6 months/year to get away from the noise. Those large buses were very noisy and I'm not so sure if they all had effective muflers. Many young school kids tried to compete with their old cars and motor bikes with modified muflers. We sold after 2 years with a $20K loss. We will try not to make the same mistake again, unless school buses and cars (used by school kids) are all electrified.

We're back on a small island, with lots of trees (without school buses), closer to the city and all the services but far enough from schools. We're no longer in the mountains but we can see many of them up to 100 Km away.

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