Average fuel consumption

In addition to the vehicle loading, the fuel consumption is determined by three main factors: traffic conditions, vehicle specifications and driver’s behaviour (Leonardi & Baumgartner 2004). Traffic conditions include road geometry and traffic flow. Road geometry affects fuel consumption mostly in hilly terrain, but also winding roads may cause braking and acceleration which increases fuel consumption. Traffic flow is affected by the number and behaviour of other road users and by the regulation of traffic flow, i.e. traffic lights, speed limits, etc. The effects of road geometry are minor compared to the effects of irregular traffic flow. The fuel consumption is lowest at average speed of around 70 km/h and the consumption increases by about 50% if the average speed reduces to 20 km/h and more than doubles with average speed of 10 km/h (JAMA 2008). A Finnish research found that the fuel consumption of an 18 ton delivery truck increased by about 33% from highway cycle to delivery cycle (Erkkilä et al. 2008). Hence, transport policy may decarbonise road freight transport by investing in road infrastructure, improving road traffic management, introducing road user charges and relaxing restrictions for night deliveries (IEA 2009). Hauliers, on the other hand, may use dynamic vehicle routing to avoid congested roads and

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negotiate with their customers to reschedule the deliveries. These measures may result in fuel savings of around 6%. (Leonardi et al. 2006, Palmer & Piecyk 2010, FTA 2012.)

Vehicle specifications affect the fuel consumption in numerous ways. Firstly, there are significant differences in the fuel consumption between the new trucks of different brands (Erkkilä et al. 2008). Unfortunately, there are no standards or tests for the fuel consumption of trucks in place in Europe, so no objective information is available for hauliers. Only Japan has introduced standards for trucks and significant reduction in fuel consumption is expected to be achieved (IEA 2007a). Historically, the fuel consumption of trucks has improved by around 1% annually, but this development may be disrupted because of the tightening limits for NOx emissions (IEA 2007a). However, there are several possibilities for improvements in truck engine and transmission, such as: downsizing, supercharging and automated manual transmission, which combined result in substantial fuel savings (RICARDO 2009, IEA 2007a). The improvement with greatest fuel saving potential is hybrid electric powertrain. Potential fuel savings range from 5% to 30% depending on the duty cycle. Greatest savings can be achieved in urban delivery operations. (RICARDO 2009.) Truck manufacturers are responsible for the development of truck powertrain, but the hauliers may decarbonise their operations by purchasing trucks with low consumption and the government can help hauliers to make the right decision by introducing fuel consumption standards. In addition to engine and transmission, there is a variety of measures which the haulier can implement to achieve considerable fuel savings. Table 5 summarises some of these measures and their potential fuel savings.

39 Table 5. Fuel saving measures and potential savings (FTA 2012, RICARDO 2009, DfT 2010a, RASTU 2009).

Potential savings

DfT 2010 RICARDO ₂₀₀₉ FTA 2012 RASTU 2009

Aerodynamics

Under-run air dam <1%

Cab roof fairing 4%

7% 4%

Cab side edge turning vanes <1%

Body/trailer side panels <1% 1%

Body/trailer front fairing 3% Tipper sheeting systems <1%

Teardrop trailer 10% 10% 6%

Sloped roof trailer 5% 5%

Reduce height of vehicle 3%

Spray suppression flaps 2% 4%

Tyres

Fuel efficient tyres (all axles) 3% 5% 2% 4%

Super single tyres 2% 6% 2%

Tyre pressure management 1% 7% 2%

Regrooving tyres 1%

Wheel alignment 4% <2%

Other

Synthetic engine oil 2% 2% <1%

Anti-idling campaign 2% 3%

Speed limited to 84 instead of 90 km/h <1% <1% 5%

Reduced vehicle own weight 1% 1% per 1t

Drivers’ driving behaviour has a great effect on fuel consumption. The difference between drivers can be up to 30% (Liimatainen 2011). Because of this, many companies have implemented ecodriving training and gained 5-15% short-term fuel savings. However, the effects of ecodriving training often decrease to about 5% in long term if the driving behaviour is not monitored and feedback is not given. (IEA 2007b.) Regular monitoring can also include an incentive system for drivers. Brown & Coyle (2004) conducted an extensive survey about drivers’ incentive systems in Great Britain. Only six companies out of 88 had an incentive system aimed at reducing fuel consumption. Two surveys from Canada show similar results. According to Barton et al. (1998) only one company out of 40 had fuel reduction incentive systems. In a latter survey by Canadian Office of Energy Efficiency OEE (2000) the figures were 10 out of 42. According to Brown & Coyle (2004) transportation companies are interested in implementing incentive systems and 58 % of the companies think that such a system would certainly or possibly be beneficial for the company. Brown & Coyle (2004) also identified some challenges facing incentive systems that are operated within transportation companies. The greatest challenges were: complexity of implementation, lack of accurate consumption data and lack of information on how to operate such a system. Monitoring drivers’ performances fairly is a complex matter. Technical issues may cause difficulties and even if these problems are solved, incentive

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systems are often criticized for unfair comparison between drivers. Unfairness is a difficult problem to solve owing to the complexity of measuring drivers’ performances. Weather, traffic, road geometry, vehicle and load carried are all constantly changing independent of a driver’s actions but each can have a considerable effect on fuel consumption. Nevertheless, current on-board computers enable taking these issues into account to establish a fair incentive system (Liimatainen 2011). Policy makers can promote ecodriving through awareness campaigns, mandatory ecodriving as part of driving license training and fiscal incentives for purchasing of on-board monitoring equipment (IEA 2007b).