Last week I had the opportunity to visit London. Hybrid Double Decker buses dominate the bus traffic in the centre of London.

Early 2009 the first 6 Volvo hybrid double decker buses (B5LH) were put into service in London. It did not take long until the first reports came. The Volvo double decker’s became top performers in reliability and fuel consumption. Since then, more than 800 hybrid buses have been put into service in the United Kingdom. Most of them are running in London.

I have collected some data from the last six years experience:

*Average total yearly speed* of the UK selection: 18.5 km/h*

*90 ^{th} percentile: 13 km/h (i.e. 90% of the buses run faster than 13 km/h)*

*10 ^{th} percentile: 26 km/h (i.e. 10% of the buses run faster than 26 km/h)*

*Average yearly distance 58 000 km*

**the speed includes all operation in service ant out of service (the criteria for accumulating fuel consumption data is that the key is turned to the “ON” position. In this way also “electric idle of hybrid buses is also included”*

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*The fuel consumption of the average bus (running at 18.5 km/h) is: 34.9 liter / 100 km*

*The fuel consumption of the 90 ^{th} percentile (running at 13 km/h) is: 41.2 liter / 100 km*

*The fuel consumption of the 10 ^{th} percentile (running at 26 km/h) is: 28.6 liter / 100 km*

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Volvo has three recent technologies for Double Decker buses in UK.

Below we compare the fuel consumption performance for the gross number of buses in the UK. It should be noted that the buses run at different operators and in different types of service. The yearly average speed alone does not full describe the bus service. However gives a strong indication for which fuel consumption can be expected for different operation.

*Table Fuel Economy, yearly average of the population here compared at an average speed of *15 km*/h. The fuel saving is calculated as how much less fuel is required for the Hybrid to achieve bus service of the same distance as the diesel buses that it is compared to.*

At lower speed the idle time increase and the fuel consumption increases for all buses.

*Table Fuel Economy, yearly average of the population here compared at an average speed of *12.5 km*/h. (there were too few B5TL buses running at the lower speed therefore significant data could not be extracted for comparing to the B5TL model at the low speed)*

12.5 km/h | miles / Gallon (UK) | Liter / 100 km | Saving to B9TL |

B5LH | 6.6 | 43 | 30% |

B9TL | 4.6 | 61 | 0% |

In the same way the fuel consumption decreases when the total yearly speed is increased. speed the idle time increase and the fuel consumption increases for all buses.

*Table Fuel Economy, yearly average of the population here compared at an average speed of 18 km/h.*

When the fuel consumption is plotted to the average speed the following graph is obtained:

As a final conclusion the following “back-of-an-envelope” calculation illustrate the impact of the hybrids in UK:

Number of Volvo Hybrid buses | 800 | fleet |

Average fuel saving | 14.88 | liter per 100 km |

Yearly distance | 58 000 | km |

Total fleet yearly saving | 6 904 | m3 |

Fleet life-time fuel saving (12 years) | 82 852 | m3 |

Fleet daily fuel saving (365 days per year) | 19 | m3 |

Fleet cost saving (£1.15 per litre) | 21 753 | £ per day |

Fleet CO2 saving (2.63 kg CO2 per litre) | 50 | tonnes per day |

*Table: Impact of hybrid bus fleet on fuel and CO2, the average bus having a speed of 18 km/h, and a fuel consumption 32.5 liter per 100 km. The average diesel bus (mix of all) has a fuel consumption of 48 liter per 100 km.*

**Now over to something completely different:** Yesterday I visited the lake of Hornborgasjön close to the Volvo Engine factory in Skövde Sweden.

The dance of the Crane birds is a spectacular event that gathers about 15 000 specimens of the Cranes (Grus Grus) and some thousands of the Homo sapiens specimen. Swans, ducks and other animals seem to be attracted to the event as well.