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‫ە‬Research Trends and Results

Simple method of investigating CO2emissions from vehicles on actualroads
DOHI Manabu, Senior Researcher
TAKIMOTO Masamichi, Researcher
SONE Shinri, HeadRoad Environment Division, Environment Department

Research Trends and Results(Key words) CO2 emissions, road traffic, road survey 
1. Background and purpose of the research
CO2 emissions by the transportation sector haveshown a falling trend in recent years, but account for
about 20% of all CO2 emissions in Japan. To reducethese emissions, it is essential to take an integratedapproach applying measures in many areas including
improving fuel performance of individual automobiles
and using alternative energy, eco-driving, switching topublic transportation, smoothing road traffic flow, andtransforming the structures of cities. In order to accurately clarify the effectiveness ofthese measures, it is necessary to make a detailed
assessment of CO2 emitted from automobiles travelingon actual roads, but because a rational survey method
to do so is not fully established, traffic volume andaverage driving speed data and CO2 emission
coefficients by speed are used to estimate CO2emissions from road traffic in specified sections. 
Under such circumstances, a method using
store-bought fuel gauges to perform simple anddetailed surveys of CO2 emissions by an automobile
traveling on an actual road was established. 
2. Outline of the simple CO2 emission survey
method using fuel gauges
The fuel gauges used for this survey were connectedto the diagnosis use connector in each automobile asshown in Photo 1, permitting the date and time,
vehicle speed, engine revolutions, fuel injection time,
GPS, and other data stored in the vehicle’s ECU to berecorded on a memory card. Based on the datacollected by this instrument, the instantaneous fuelconsumption per second and CO2 emissions wereestimated. 
The instantaneous fuel consumption is proportional
to the engine revolutions and fuel injection time. The
total fuel consumption, which is the total of theinstantaneous fuel consumptions, was corrected using
the quantity of actual fuel supplied to eachautomobile’s fuel tank before and after the survey as
the positive value. The CO2 emissions were converted
from the quantity of fuel consumption, a technique
identical to the method used to calculate thegreenhouse effect gas national inventory.

 Figure 1 shows an example of survey results. Thissurvey method can clarify behavior of automobile CO2
emission behavior before and after an intersection. In
this case, the CO2 emissions were high during idlingwhile the vehicle was stopped in front of theintersection and during acceleration after passing
through the intersection.
 We aim to continue to accumulate results of surveys
using various vehicles and under various driving
conditions to provide this survey method for generaluse.

Fuel gauge/GPS

Connected to diagnosis use connector Photo 1. View of Installation of Fuel Gauge in anAutomobile
Connected to the diagnosis use connector at the driver’s seat to collectvehicle data
CO2 emissions (unit: g)ͤ Emissions per second
except when shut off.

Figure 1. Distribution of CO2 Emissions Turning
Right at an Intersection

CO2 emissions are large during idling and while accelerating after aright turn[Sources]
M. Dohi, S. Sone, M. Takimoto: Simple investigationof CO2 emissions from road traffic and its variationaccording to differences of road structure, Selected
Papers on Environmental Systems Research, vol. 38,
2010‫ە‬Research Trends and Results