DriveGain analysis: Reducing maximum speed to 60 MPH reduces fuel consumption by 10%, but only adds 2 minutes to journey time
June 27th 2012, London, UK – DriveGain, the company that produces the iPhone application that helps you save fuel as you drive, has analysed the 10,000 journeys uploaded to the DriveGain web portal over the last 9 months.
“We found that limiting your maximum speed to 60 MPH reduces your fuel consumption by 10%,” said Simon East, CEO of DriveGain, “but that this only adds 2 minutes to the average journey time”.
“We find drivers tend to over-estimate how much quicker they will arrive when driving faster”, he added. “Unless the roads are totally clear, other traffic on your route will tend to slow you down considerably. Drivers are wasting a lot offuel for very little difference in their arrival time”.
When driving at higher speeds drivers tend to accelerate until they catch up with traffic ahead, at which point they brake to slow down, and this constant acceleration and braking cycle uses much more fuel than travelling at a constant speed.
Even reducing the maximum journey speed to 70 MPH has real benefits: fuel consumption is reduced by 6% but journeys only take a minute longer on average.
The table below summarises DriveGain’s findings on the effects of restricting journeys to sets of speeds in MPH:
| Speed restricted to | 50 MPH | 60 MPH | 70 MPH |
| Average extra journey time (s) | 233 | 121 | 53 |
| Fuel saved (%) | 15% | 10% | 6% |
| MPG increase (UK) | 6.3 | 4.0 | 2.2 |
| MPG increase (US) | 5.2 | 3.4 | 1.8 |
| litres/100km reduction | 1.1 | 0.8 | 0.4 |
The DriveGain application uses the iPhone’s GPS to calculate how efficiently the vehicle is being driven. Combining information about the rates of acceleration, driving smoothness, and overall speed with the exact specifications of your car, DriveGain gives the driverfeedback on how they can reduce the amount of fuel they are using.
The basic version of the app is available for free, offering a MPG reading and a Journey Score out of 100 for each trip. Additional displays like the Cost Meter and Fuel Savings Meter can be purchased as add-ons. For example the Fuel Savings Meter this driver was using cost just £1.49.
DriveGain can be downloaded from Apple’s App store here:http://itunes.com/apps/drivegain
How DriveGain analyses journey data
For each journey the DriveGain app records the actual fuel used and the journey duration. In addition it also simulates of how much fuel would have been used, and the resulting journey time, had thedriver limited their maximum speed to a set of MPH and km/h values. This journey data is uploaded to the web server (for users who enable this) where it can be analysed.
DriveGain analysis using restricted speeds in km/h
For countries that use metric speeds we repeated the process above with a set of speeds in km/h:
| Speed restricted to | 80 km/h | 100 km/h | 120 km/h |
| Average extra journey time (s) | 237 | 105 | 37 |
| Fuel saved (%) | 15% | 9% | 4% |
| MPG increase (UK) | 6.3 | 3.7 | 1.7 |
| MPG increase (US) | 5.2 | 3.1 | 1.4 |
| litres/100km reduction | 1.1 | 0.7 | 0.3 |
