Paper No. 06-2567

Estimation of Fuel Use by Idling Commercial Trucks

By

Linda Gaines

(630) 252-4919 E-mail: lgaines@anl.gov

Anant Vyas

(630) 252-7578 E-mail: avyas@anl.gov

John L. Anderson

(630) 252-6510 E-mail: jlanderson@anl.gov

Center for Transportation Research

Argonne National Laboratory

9700 South Cass Avenue

Argonne, Illinois 60439

Submitted for presentation at and inclusion in the compact disc of the

85th Annual Meeting of the

Transportation Research Board

Washington, D.C.

January 22–26, 2006

Word Count: Text – 6,137; Three Figures – 750; Two Tables – 500. Total Word Count – 7,387

The submitted manuscript has been created by the 

University of Chicago as operator of Argonne National 

Laboratory (“Argonne”) under contract No W-31-109-

ENG-38 with the U.S. Department of Energy. The U. S. 

Government retains for itself, and others acting on its 

behalf, a paid-up, nonexclusive, irrevocable worldwide 

license in said article to reproduce, prepare derivative 

works, distribute copies to the public, and perform publicly 

and display publicly, by or on behalf of the Government.
L. Gaines, A. Vyas, and J.L. Anderson 1

Estimation of Fuel Use by Idling Commercial Trucks

Linda Gaines, Anant Vyas, and John L. Anderson

Center for Transportation Research

Argonne National Laboratory

Argonne, IL 60439

ABSTRACT

This paper uses the recently published 2002 Vehicle Inventory and Use Survey 

(VIUS) to determine the number of commercial trucks in the categories that are 

most likely to idle for periods of over 0.5 h at a time. On the basis of estimated 

numbers of hours for both overnight idling by sleepers and long-duration idling 

by all size classes during their workdays, the total fuel use by idling trucks is 

estimated to be over 2 billion gallons per year. Workday idling is determined to 

be a potentially much larger energy user than overnight idling, but data are 

required before any definitive conclusions can be reached. Existing technologies 

can reduce overnight idling, but development may be needed to reduce workday 

idling.

INTRODUCTION

Idling of heavy vehicles, in particular trucks, has become a subject of great interest in the past 

few years because of the large quantity of petroleum used and emissions created without any 

productive movement of goods accomplished. (In 2000, for example, Argonne National 

Laboratory [Argonne] estimated that over 800 million gallons of diesel are used annually just for 

overnight idling of sleeper cabs [1].) Recent milestones include a U.S. Department of Energy 

(DOE) report published in 2000 (1), the inclusion of idling reduction in the 2001 National 

Energy Policy (2), and the 2004 National Idling Reduction Planning Conference. Of special 

interest recently was a series of regional workshops held by the U.S. Environmental Protection 

Agency (USEPA) in an attempt to help states harmonize their inconsistent idling regulations. 

Because this topic has aroused such broad interest, published information spreads rapidly 

and is often quoted (and misquoted) widely. Our previous estimate of the number of trucks that 

might idle overnight (1), which was based on the 1997 Vehicle Inventory and Use Survey 

(VIUS) (3), found its way into numerous documents. However, in 2004, long after that work was 

completed, the 2002 VIUS (4) became available, and we use this paper to provide an updated 

and carefully documented estimate based on the 2002 VIUS. In addition, since many trucks idle 

for long periods during working hours, we will also estimate the contribution of non-overnight 

idling to total idling fuel use.

TRUCK CATEGORIES

Trucks are classified in eight gross-vehicle-weight (GVW) classes. Gross vehicle weight means 

empty vehicle weight plus cargo weight. The classes were formulated over 50 years ago when 

truck transport was not very prevalent. The eight classes are shown in Figure 1. Note that the 

USEPA and National Highway Traffic Safety Administration (NHTSA) subdivide class 2 into 
L. Gaines, A. Vyas, and J.L. Anderson 2

2A (6,001–8,500 lb) and 2B (8,501–10,000 lb) for 

regulatory purposes (emissions and fuel economy).

Data Sources

Two public data sources are often used for trucks:

i. The Federal Highway Administration’s 

(FHWA’s) Highway Statistics and 

ii. The Bureau of the Census’ VIUS. 

The FHWA publishes Highway Statistics annually, 

while the VIUS is conducted every five years in the 

calendar years ending in 2 and 7. The last VIUS was 

conducted in 2002. The Highway Statistics provides 

truck population, vehicle miles, and fuel use data for 

three types of trucks: 

i. Trucks with two axles and four tires, 

ii. Single-unit trucks with six tires or more, and 

iii. Combination trucks. 

The VIUS data provide detailed information related to 

over 200 attributes of each sampled truck. The 

2002 VIUS provides data on 80 million class 1 and 

2 trucks and 4 million single-unit trucks, including 

personal-use vehicles, plus data on 1.4 million 

combination trucks in GVW class 3–8 (4). The 

Highway Statistics give data on 85 million two-axle, 

four-tire trucks; 5.7 million other single-unit trucks; 

and 2.3 million combination trucks (6). Because the 

VIUS data give more information than is necessary for 

our analysis, we will use it VIUS data in this paper. 

Our analysis also excludes trucks that were not in use while the survey was conducted. Figure 2a 

shows commercial truck populations, and Figure 2b shows commercial truck fuel use by class. 

Note that the large numbers of trucks that are personal-use vehicles have now been excluded. 

Even with those vehicles removed, the smallest and largest classes dominate both fuel use and 

numbers of vehicles and therefore should be the focus. Classes 1–3 use both gasoline and diesel 

fuel; higher classes use almost exclusively diesel. The abbreviations SU and C refer to singleunit trucks and combinations (tractor-trailers), respectively.

The 2002 VIUS provides information related to truck type, truck body type, trailer type, 

and trailer configuration for combination trucks; model year; annual miles; fuel economy in 

miles per gallon (MPG); average weight; empty weight; percentages of annual miles in trips of 

different length; and many other attributes. Each sampled truck is assigned to a GVW class on 

the basis of two different ways: (i) average weight and (ii) the truck’s vehicle identification 

number (VIN). The Census Bureau summaries are by average weight-based GVW class. We 

FIGURE 1 Truck Classes (5).
L. Gaines, A. Vyas, and J.L. Anderson 3

0

1

2

3

4

5

6

7

8

1 2A 2B 345 6SU 6C 7SU 7C 8SU 8C

GVW class

number of trucks (millions)

diesel

gasoline

0

2

4

6

8

10

12

14

16

1 2A 2B 345 6SU 6C 7SU 7C 8SU 8C

GVW class

fuel use (billion gallons)

diesel

gasoline

FIGURE 2a Number of commercial trucks FIGURE 2b Fuel use by commercial trucks

(class 1-8). (class 1-8).

also use the average weight-based GVW classes in our analysis to be consistent. The sampling 

frame design measures of sampling variability and coefficients of variation in the 2002 VIUS are 

described in reference 7. The mircrodata compact disc of the 2002 VIUS was released in early 

2005, and so the survey represents the latest data related to the nation’s trucks.

A sampled truck’s annual miles are assigned to trips of different length, grouped by five 

distance ranges: 

• 50 miles or less, 

• 51–100 miles, 

• 101–200 miles, 

• 201–500 miles, and 

• More than 500 miles.

The Census Bureau created a primary trip range field for each sampled truck by selecting the 

group with the highest percentage. If the highest value occurred in more than one group, the 

primary trip range was selected randomly. For example, if a truck tractor with sleeper cab has its 

annual miles distributed as 10% in 101–200-miles group, 45% in the 201–500-miles group, and 

45% in the more-than-500-miles group, it could be assigned either to the 201–500-mile group or 

the more-than-500-mile group. Also, a truck assigned to a group in the less-than-500-miles range 

could also have some (or substantial) miles in trips of over 500 miles. Aside from analysis by 

percentage annual miles in various distance groups, we also analyze annual miles to identify 

trucks that travel long distances. 

The 2002 VIUS data file contains 98,682 records, of which 3,250 records are for “Not in 

Use: trucks that have zero VMT. The number of useful records is therefore 95,432. Out of these 

useful records, 18,053 records do not have any MPG information. We first summarized the 

77,379 records that have MPG information and created a lookup table by two variables: 

(i) average weight-based GVW and (ii) body type. The average known MPGs from this lookup 

table were assigned to the 18,053 records that did not have any MPG information. This MPG 

information is used for computing fuel consumption by various categories of trucks.

Light Trucks

Almost all trucks with GVW less than 10,000 lb have two axles and four tires (8) and are 

classified as light trucks. A majority of these light trucks (83%) are used for personal 

transportation (4). Excluding trucks that are not in use, 13.3 million light trucks are used for 
L. Gaines, A. Vyas, and J.L. Anderson 4

commercial purposes. These trucks fall in four categories: (i) pickup, (ii) minivan, (iii) sport 

utility vehicle, and (iv) full-size van. Nearly 97.5% of personal-use light trucks are gasolinepowered, while 89.3% of commercial light trucks are gasoline-powered. The top five types of 

businesses using these trucks are (i) construction; (ii) services; (iii) agriculture, forestry, fishing, 

hunting; (iv) retail trade; and (v) manufacturing. The services category includes information 

services; waste management, landscaping, or administrative/support services; arts, entertainment, 

or recreational services; accommodation or food services; and other services. Together, these 

five business types use 76% of all commercial light trucks.

Single Unit Heavy Trucks

The single unit trucks in GVW class 3–8 have several body types. The top five body types 

ranked by truck population are (i) flatbed/ platform, (ii) pickup, (iii) dump, (iv) basic enclosed 

van, and (v) step or multi-stop van. These five body types account for 68% of the single unit 

trucks in GVW class 3–8. The same five body types rank among the top five by fuel use, but not 

in the same sequence. The rankings by fuel use are (i) dump, (ii) basic enclosed van, (iii) flatbed/ 

platform, (iv) pickup, and (v) step or multi-stop van. Together, these five body types account for 

62% of the fuel use by single unit trucks in GVW class 3–8. In terms of fuel economy, the five 

least-fuel-efficient single-unit body types are (i) concrete mixer, (ii) low boy, (iii) trash/ garbage, 

(iv) open-top van, and (v) pole/logs/pipe. Together, these five least-fuel-efficient trucks account 

for 23% of the fuel consumption by Class 3–8 single unit trucks with only concrete mixer (no. 9) 

and garbage trucks (no. 6) ranked among the top 10 fuel consumers.

Combination Trucks

Among truck tractors, 666,300 have cab sleepers and 721,900 do not. Nearly 500,000 of the 

sleepers have some part of their annual VMT in trips of longer than 200 miles, while nearly 

210,000 non-sleepers have some part of their VMT in trips of over 200 miles.

Newer (model year 1997 and later) truck tractors with sleepers total 407,000, average 

107,000 miles/year, and have 63% of annual miles in trips over 200 miles. Common carriers and 

owner operators use their sleepers more intensively, with truck tractors of model year 1995 and 

newer for common carriers and model year 1991 and newer for owner operators averaging more 

than 60,000 annual miles per vintage. Such sleepers total 296,300 for common carriers and 

128,600 for owner operators. The intensively used older sleepers, not included in the 407,000 

mentioned above, total 96,000, average 74,270 miles/year, and have 57% of annual miles in trips 

over 200 miles. When added to the above 407,000 newer model (1997 and later) sleepers, the 

sum exceeds 500,000. We also analyzed sleeper trucks by annual miles traveled. Sleepers 

traveling over 80,000 miles/year total 380,000, average 119,000 miles/year, and have nearly 65% 

of their annual miles in trips longer than 200 miles. An additional 76,000 sleepers have 

60,000–80,000 annual miles, and 46% of these miles involve trips longer than 200 miles. These 

two groups sum to 456,000 sleepers. Some more sleepers in the 40,000–60,000-annual-mile 

category would idle overnight because they average over 50,000 miles/year and 34% of miles 

traveled are for trips longer than 200 miles. Paul Abelson of LandLine magazine (9) used his 

technical judgment of the probability of overnight idling for sleeper trucks by trailer type and 

estimated that over 490,000 sleepers would idle overnight. Thus, by several different lines of 

reasoning, nearly half a million sleepers travel long distances, are subjected to the 11 hours/day 

and 8 days/70 hours-of-service rules, and are likely to idle overnight if an alternative supply of 

hotel power is not available.
L. Gaines, A. Vyas, and J.L. Anderson 5

Some 91,000 truck tractors without a sleeper cab have over 40% of their annual miles in 

trips longer than 200 miles, and another 129,000 tractors have lesser percentages of annual miles 

in trips longer than 200 miles. In terms of annual miles, 139,000 non-sleeper truck tractors have 

over 80,000 annual miles, average 113,000 miles/year, and have 29% of their annual miles in 

trips longer than 200 miles. When on overnight trips, the drivers of these non-sleeper trucks will 

have to rest somewhere outside and return to the truck after rest. A majority of non-sleeper truck 

tractors (512,000) are employed in short trips and may idle while waiting for loading/unloading 

and during stops for meals and other breaks. In terms of average annual miles, 400,000 such 

trucks travel over 50,000 miles, with 23.4% of annual miles in trips longer than 200 miles. An 

additional 113,000 truck tractors travel 40,000–50,000 miles annually. The five most often 

pulled trailers are (i) the basic enclosed van, (ii) the dump, (iii) the flatbed/platform, (iv) the low 

boy, and (v) the tanker for liquid or gas. They account for 77% of the non-sleepers. The five

tractors that have the highest fuel consumption are (i) the basic enclosed van, (ii) the dump, 

(iii) the tanker for liquid or gas, (iv) the flatbed/platform, and (v) insulated refrigerated van. They 

account for 82% of the fuel consumption by non-sleepers.

TRUCK IDLING

The type of truck idling that has received the most attention has been that of sleeper cabs, parked 

overnight at truck stops, rest areas, or by the side of the road, with the engine left on to keep the 

sleeping driver comfortable and to keep the engine fluids warm and the batteries charged. Of 

course, only drivers of sleepers, generally class 8C trucks (see below), are likely to engage in this 

type of behavior. Several technical options that can be installed on trucks, such as small heaters 

and auxiliary power units (APUs), are available to provide the services needed when the main 

engine is shut off. In addition, electrical plug-in options are available at some truck stops and 

depots. These are described in Stodolsky et al. (1) and listed on the EPA Smartway web site (10).

Another type of idling is done by various vocational trucks during their workdays. These 

trucks are using their main engines to accomplish work other than moving the vehicle down the 

road. Examples include cement mixers that rotate and asphalt trucks that heat their loads to keep 

it from getting too viscous. The industry term for this kind of application is “power take-off” (or 

PTO). We do not include PTO in the accounting of truck idling because useful work is being 

accomplished. 

The third type of idling is important but has not as yet been evaluated to see how much 

energy is being used. It is most succinctly described as “waiting” and can be divided into 

two categories, depending on whether the truck is simply parked or waiting in a queue, needing 

to move forward every few minutes to maintain its place in the line. The term for waiting in a 

line is “creep mode.” Note that these categories exclude time during travel from place to place 

when the truck is stuck in traffic and must idle. The trucks that are simply parked could utilize 

the same devices as the overnight idlers if no comfortable waiting place were available for the 

drivers. Trucks in a line would require some alternative to restarting the engine frequently if this 

idling were to be avoided. Possibilities include scheduling, delicatessen-style numbers, and 

engineering to use APUs to power creep mode. 

Overnight Idling

Although there may be cases of trucks idling overnight for other reasons, by far the most 

common reason is that the driver is sleeping in the vehicle and requires heat or air conditioning 
L. Gaines, A. Vyas, and J.L. Anderson 6

and electricity to stay comfortable. Drivers remain in their sleeper compartments to sleep and 

relax during the off-duty periods required by the federal hours-of-service regulations. It is not yet 

known how recent changes in these regulations will affect total idling time. By definition, and by 

law, this type of idling is limited to those trucks that have sleeper compartments; almost all of 

these are class 8C (combinations), but there are some in classes 6 and 7 as well.

Even if the air temperature is moderate, the driver may leave the engine idling because 

open windows invite intrusions and let in polluted air and noises from other trucks. The number 

of hours varies greatly, from those drivers who get the truck warm, turn it off, and then curl up 

under heavy blankets for the night, to those who claim they never turn their trucks off for fear 

they will not start again. A survey conducted at truck stops by the University of California at 

Davis showed a broad distribution from about 500 hours/year, up to over 3,500 (see Figure 3, in 

which the horizontal axis is hours/yr idled, and the vertical axis is number of trucks).

Truckers report idling from 1 to 

10 hours per day. This is consistent with 

the typical 6 hours per day estimated by the 

American Trucking Associations and the 

1,800 hours/year estimated by Caterpillar 

as the result of an informal survey it 

performed (11). However, although 

overnight idling has been discussed often, 

no good statistical data exist, and this work 

will perform a sensitivity analysis on this 

important parameter, around a baseline 

estimate of 6 hours per day, 300 days per 

year. Use of auxiliary power units and other idling-reduction devices could eliminate most of this 

overnight idling.

The 2002 VIUS reports over 665,000 sleepers in use, and almost 60% of these travel over 

80,000 miles per year (or 270 miles/day for 300 days). Note that we are using miles per year here 

rather than distance traveled because the distance-from-home field in VIUS is actually defined as 

trips that are a given distance from the home base and may not actually reflect trip lengths. The 

trucks that travel the longest distances in a year travel the farthest each day and are most likely to 

be idling overnight, but if a truck’s route is short and includes several stops each day, the driver 

can run out of hours far enough from home to have to rest in the truck. We therefore estimated 

overnight idling hours for a conservative case by assuming that trucks going over 80,000 miles 

annually idled 6 hours/day, 300 days/year, and those traveling 60,000–80,000 miles idled 70% of 

that time; 40,000–60,000 miles, 40% of that time; and under 40,000 miles, 10% of that time. 

Trucks without sleepers are assumed not to idle overnight, and idling fuel use was assumed to be 

0.8 gal/h. On the basis of these estimates, total fuel use for idling overnight is about 685 million 

gallons. Table 1 shows fuel use by distance classes and trailer type. The fuel use of Class 6 and 

7 sleepers is shown to be negligible.

Note that team drivers can drive through the night, so a more detailed analysis should 

include information on teams and exclude overnight idling for them. Because no comprehensive 

data exist on idling hours, we performed a simple sensitivity analysis to several parameters. To 

get an upper bound on the fuel used by overnight idling, we considered all sleepers idling 

10 hours/day at 1 gallon/hour. This value triples the conservative estimated fuel use to almost 

2 billion gallons and is clearly unrealistic. However, the high degree of uncertainty associated 

0

25

50

500

1000

1500

20002500

30003500

4000

4000+

Hours per Year

Number of Trucks

FIGURE 3 Range of idling times reported (12).
L. Gaines, A. Vyas, and J.L. Anderson 7

with assumptions highlights the need to get better data on actual overnight idling practice. 

Onboard computers could be used to collect these data.

Idling as Part of the Working Day

Although it is well known that trucks often idle in the course of the workday, no detailed analysis 

exists. We will give some examples of situations in which trucks generally idle for extended 

periods, either at rest or in creep mode, and provide rough estimates of the time and energy use 

for these examples. Again, we will perform sensitivity analysis to gain some insight into whether 

this workday idling is a significant contributor to total energy use by idling trucks.

TABLE 1 Fuel Used while Idling for Sleeper Trucks, by Selected Body Types and Miles Driven 

Category

Class 8C 

w/Sleeper

(Body Type)

Miles Driven

Category (mi/yr)

Number of

Trucks

Total Fuel Used

(gal/yr)

Idle Time

per Truck

(h/yr)

Fuel Used

to Idle

(gal/yr)/trk

Fuel Used

to Idle

(gal/yr)

iIdle %

of Total

Fuel Used

Dump < 40,000 20,535 46,014,662 0 0 0 0.0

40,000–60,000 3,797 35,481,756 720 576 2,187,072 6.2

60,001–80,000 4,872 65,079,191 1,260 1,008 4,910,976 7.5

> 80,000 7,233 145,494,922 1,800 1,440 10,415,520 7.2

Flatbed/platform < 40,000 31,666 91,204,132 0 0 0 0.0

40,000–60,000 14,840 142,730,487 720 576 8,547,840 6.0

60,001–80,000 15,105 205,347,095 1,260 1,008 15,225,840 7.4

> 80,000 41,132 852,593,119 1,800 1,440 59,230,080 6.9

Tank — liguid/gas < 40,000 6,724 24,066,861 0 0 0 0.0

40,000–60,000 4,055 36,194,736 720 576 2,335,680 6.5

60,001–80,000 4,523 53,669,123 1,260 1,008 4,559,184 8.5

> 80,000 20,916 392,994,386 1,800 1,440 30,119,040 7.7

Basic enclosed van < 40,000 34,239 129,082,598 0 0 0 0.0

40,000–60,000 25,541 235,177,541 720 576 14,711,616 6.3

60,001–80,000 33,500 400,281,941 1,260 1,008 33,768,000 8.4

> 80,000 213,425 4,225,423,766 1,800 1,440 307,332,000 7.3

Insulated reefer < 40,000 5,914 21,147,647 0 0 0 0.0

40,000–60,000 5,458 53,092,054 720 576 3,143,808 5.9

60,001–80,000 7,293 93,097,435 1,260 1,008 7,351,344 7.9

> 80,000 59,659 1,350,114,617 1,800 1,440 85,908,960 6.4

Other * < 40,000 42,166 101,965,371 0 0 0 0.0

40,000–60,000 11,839 116,466,377 720 576 6,819,264 5.9

60,001– 80,000 10,257 145,308,684 1,260 1,008 10,339,056 7.1

> 80,000 34,917 747,101,232 1,800 1,440 50,280,480 6.7

Class 8C w/sleeper totals 659,606 9,709,129,733 657,185,760 6.8

Class 7C w/sleeper totals 4,802 45,830,198 1,800 1,440 6,914,880 15.1

Class 6C w/sleeper totals 1,652 23,364,721 1,800 1,440 2,378,880 10.2

* Other includes beverage, curtainside, low boy, pole, dry bulk tank, insulated non-reefer, open top, car carrier, livestock, mobile 

home toter, drop frame, unknown.
L. Gaines, A. Vyas, and J.L. Anderson 8

It is necessary to disaggregate trucks into categories based on the type of service they 

perform and to examine their daily operations. First consider the large trucks that move raw 

materials, intermediate products, and final consumer goods around the country to and from ports 

and production plants to distribution centers, retail outlets, and construction sites. Drivers of 

these trucks may need to park and find the right person to process paperwork, obtain a dock 

assignment, wait in line for their turn at the loading dock, then wait again while goods are 

unloaded from or loaded onto their trucks, check the load, and complete more paperwork when 

they are done. The time involved varies by location, time of day, and type of operation, but it can 

be from 0.5 hour to as long as 6 hours for a single stop. Similarly, trucks can be delayed in 

queues at border crossings for as long as 4 hours. 

Several measures are being used or could be developed to reduce this wasteful idling time. 

First, many companies (like Wal-Mart) use a technique known as “drop and hook” to avoid the 

delay caused by the need to wait while trailers are being loaded or unloaded. If the entire trailer 

load is going to this site, the truck driver can back the trailer into the loading dock and separate 

the tractor from the trailer, leaving the tractor free to pick up another trailer and proceed on its 

way. This type of operation requires more trailers than tractors. If only part of the load is for the 

site, the driver must wait until that part is unloaded before proceeding to the next stop on his/her 

route. 

Another technique that can be used is scheduled pick-up or delivery times. This technique 

is being tried at the Port of Long Beach. However, real-time electronic communication is 

required for this to work well. Otherwise, delays on route can cause drivers to miss their 

scheduled slots. For locations without scheduling, it would be possible to avoid queues of trucks

in creep mode by instituting a take-a-number system, similar to that used in delicatessens. 

Drivers could then park, turn off their engines, and wait in comfortable areas (such as some 

shippers already provide) until their numbers were called. Even border crossings could provide 

this service.

Another situation in which long-duration (>0.5 hour) idling occurs spans a wide class of 

vehicle service types. Almost all drivers have an hour off for lunch; during this time, the vehicle 

may be left idling, especially if the weather is warm. One expert writes, “Remember, the cab sits 

on top of a 500–800 lb heat sink that could be over 200oF. On a 50–60o day, the cab can be like 

an oven after sitting for 20–30 minutes.” (9) This problem becomes less severe for smaller 

vehicles.

Another class of vehicles that idles for significant periods during the workday is dump 

trucks, which idle while being loaded, are then driven to the dump site where they dump their 

loads, and return to be reloaded, subsequently repeating the process. Depending on the operation, 

it might be reasonable to shut the engine off during loading. This might require a climate control 

system independent of the main engine for operation in extreme weather. 

Next we consider smaller vehicles. As a general rule, smaller vehicles are easier to start, 

warm up faster, and are more likely to be stolen, so they are less likely to be left idling when the 

driver is not in them. However, some types of trucks have been observed to idle for significant 

periods when making deliveries or performing other jobs. These include leased refrigerated 

straight trucks, bakery trucks, and linen-supply company trucks (often walk-in vans), which idle 

from 10 minutes to one hour at a time. Similarly, heavy vocational straight trucks, including 

refuse haulers, public works crew trucks, and newspaper delivery trucks, may idle for 

20–30 minutes at each stop (13). Utility trucks idle as well, sometimes most of the day, but at 

least in some cases, these are providing a useful service by creating a place for workers to warm 
L. Gaines, A. Vyas, and J.L. Anderson 9

up when they come down from utility poles or up out of manholes. For such situations, heaters or 

APUs could provide the same service with less energy use and emissions. Other than these utility 

vehicles, we have not identified instances where small trucks are idled for long periods. The 

owners of the many pickups and vans that perform household and commercial repairs and 

installations or transport produce from small farms all seem to recognize how much money they 

save by simply turning their vehicles off when not in use.

Fuel Use for Workday Idling

Given these general observations and essentially no actual data, we did some simple modeling to 

determine to what extent extended workday idling could be an important problem. The short 

answer is that, given the large numbers of vehicles potentially involved, the fuel use for this type 

of idling could be much larger than that for overnight idling, and data should be obtained. This 

section details the assumptions made in order to scope out the energy use for extended workday 

idling.

We first had to estimate the per-hour fuel use for extended idling. The only data point we 

have is that idling large sleeper tractors use approximately 0.8 gal/h (or more depending on idle 

speed and accessory loads). We assumed that smaller trucks would use proportionately less fuel 

at idle; thus, if a vehicle class achieved twice the fuel economy as a class 8 tractor, it would burn 

half as much fuel at idle (0.4 gal/h). 

We then had to estimate the idling hours for different types of trucks. This estimate was 

highly uncertain. We identified several classes of trucks that might idle for extended periods and 

estimated the possible extent of idling. Our first attempt assumed that all vehicles of that type 

idled for the maximum time; these estimates did not seem reasonable, so we revised our numbers 

downward on the basis that (i) only a subset of the vehicles were high idlers or (ii) the need was 

only present part of the year. In each case, we assumed that the vehicles that traveled the longest 

distances spent most of their time on the road, and those that traveled under 40,000 miles per 

year were driven less because much of the time, they were stopped waiting for something or 

someone and were idled most. We assigned the maximum idling hours to the under-40,000-mile 

trucks, 75% of maximum to those driven 40,000–60,000 miles, 50% to those driven 

60,000–80,000 miles, and 25% to those driven more than 80,000 miles. In each case, we 

assumed that the vehicle operated for 300 days per year and estimated a typical number of hours 

idled per day for the body type. Vans and dump trucks were assigned 2 hours/day; utility 

vehicles, 3 hours/day; platform trucks, tankers, and garbage trucks, 1 hour/day; and all other 

trucks, 0.5 hour/day. As shown in Table 2, even these relatively conservative estimates yield a 

total fuel use of almost 2.5 billion gallons annually (7% of the fuel used by these trucks), leading 

us to conclude that idling during the workday consumes a significant amount of fuel and should 

be examined in detail. 

Table 2 was constructed by identifying types of trucks that were likely to idle and 

specifically adding hours for them over an assumed low baseline. However, the idling hours by 

some delivery vans could be underestimated, and accounting for increased idling by those 

numerous large trucks would significantly increase the total. Similarly, it would be appropriate to 

identify types of trucks, such as pickups, for which we could not identify any reason to idle 

routinely and subtract these types of trucks. Subtracting pickup trucks reduced the first estimate 

by almost 500 million gallons per year because of the large number of pickups in commercial 

service (over 7 million). This modification illustrates the high degree of sensitivity of these 
L. Gaines, A. Vyas, and J.L. Anderson 10

results to individual inputs. It is clear that actual data on idling practices of trucks during the 

workday must be sought.

TABLE 2 Fuel Used by Commercial Trucks Idling on the Job by Selected Body Type and Miles 

Driven Category

All Commercial

Body Types

Miles Driven

Category (mi/yr)

Number of

Trucks

Total Fuel Used

(gal/yr)

Ave.

mpg

Idle

Time

(h/yr)

Idle Fuel

Flow Rate

(gal/h)

Fuel Used

to Idle

(gal/yr)/trk

Fuel Used

to Idle

(gal/yr)

Idle as x%

of Total 

Fuel Used

Minivan < 40,000 1,175,532 1,038,768,478 17.7 600 0.262 157 184,897,237 17.8

40,000–60,000 65,009 178,620,070 17.7 450 0.262 118 7,668,858 4.3

60,001–80,000 17,384 86,127,314 13.0 300 0.357 107 1,861,425 2.2

Full-size (LD) van < 40,000 2,040,986 2,040,445,188 13.2 600 0.352 211 430,462,502 21.1

40,000–60,000 69,063 240,504,381 13.1 450 0.354 159 11,007,904 4.6

> 80,000 9,400 51,618,036 17.3 150 0.268 40 378,173 0.7

Dump < 40,000 724,547 1,019,392,773 5.8 600 0.800 480 347,782,560 34.1

40,000–60,000 49,005 490,693,938 4.9 450 0.947 426 20,882,131 4.3

60,00–80,000 23,529 326,154,539 5.1 300 0.910 273 6,422,033 2.0

> 80,000 23,977 483,093,921 5.3 150 0.875 131 3,148,678 0.7

Flatbed/platform < 40,000 939,658 1,217,696,747 7.4 300 0.627 188 176,757,289 14.5

40,000–60,000 49,334 370,892,077 6.4 225 0.725 163 8,047,609 2.2

60,00–80,000 25,770 321,901,976 5.7 150 0.814 122 3,146,653 1.0

> 80,000 50,924 1,012,165,598 5.6 75 0.829 62 3,164,563 0.3

Service – utility < 40,000 248,756 368,030,625 7.7 900 0.603 542 134,909,748 36.7

40,00–60,000 4,924 28,084,098 8.2 675 0.566 382 1,880,728 6.7

60,00–80,000 718 4,313,840 11.3 450 0.411 185 132,671 3.1

> 80,000 913 8,736,854 10.3 225 0.450 101 92,541 1.1

Tank – liquid/gas < 40,000 177,128 379,586,263 5.5 300 0.844 253 44,829,487 11.8

40,000–60,000 16,329 143,096,007 5.7 225 0.814 183 2,990,785 2.1

60,001–80,000 12,016 146,697,628 5.9 150 0.786 118 1,417,481 1.0

> 80,000 35,401 673,812,671 5.9 75 0.786 59 2,088,059 0.3

Trash/garbage < 40,000 77,520 305,197,033 4.4 300 1.055 316 24,524,509 8.0

40,000–60,000 12,016 119,502,504 5.0 225 0.928 209 2,508,941 2.1

60,001–80,000 2,733 35,901,942 5.2 150 0.892 134 365,802 1.0

> 80,000 949 18,234,173 5.9 75 0.786 59 55,975 0.3

Basic enclosed van < 40,000 650,517 1,469,253,265 7.3 600 0.636 381 248,087,579 16.9

40,000–60,000 107,404 817,171,943 6.5 450 0.714 321 34,501,470 4.2

60,001–80,000 94,550 1,052,739,306 6.3 300 0.737 221 20,891,048 2.0

> 80,000 302,672 5,873,032,985 6.1 150 0.761 114 34,534,379 0.6

Insulated reefer < 40,000 96,268 292,236,464 6.7 600 0.693 416 40,001,509 13.7

40,000–60,000 20,414 161,964,407 6.2 450 0.748 337 6,874,908 4.2

60,001–80,000 17,325 202,947,017 6.0 300 0.773 232 4,019,400 2.0

> 80,000 70,694 1,556,874,982 5.6 150 0.829 124 8,786,254 0.6

Multi-stop van < 40,000 372,892 662,599,461 8.6 600 0.540 324 120,712,945 18.2

40,000–60,000 17,268 84,280,278 9.6 450 0.483 218 3,755,790 4.5

60,001–80,000 3,077 24,132,931 8.5 300 0.546 164 503,904 2.1

> 80,000 1,265 11,870,995 10.1 150 0.459 69 87,172 0.7

Other van < 40,000 54,471 77,343,236 8.8 600 0.527 316 17,232,644 22.3

40,000–60,000 1,193 5,713,537 9.6 450 0.483 218 259,478 4.5

60,001–80,000 513 3,062,867 11.2 300 0.414 124 63,759 2.1

> 80,000 377 3,480,504 10.9 150 0.426 64 24,073 0.7

Drop frame < 40,000 6,304 18,859,832 6.2 600 0.748 449 2,830,699 15.0

40,000–60,000 1,810 14,755,498 5.9 450 0.786 354 640,556 4.3

60,00–80,000 1,364 15,423,848 6.3 300 0.737 221 301,379 2.0

> 80,000 4,502 102,985,261 6.0 150 0.773 116 522,232 0.5

Other < 40,000 9,829,988 9,827,530,297 13.7 150 0.339 51 499,392,091 5.1

40,00–60,000 503,006 1,842,295,205 12.5 112 0.371 42 20,912,173 1.1

60,001–80,000 65,680 579,037,170 7.8 75 0.595 45 2,930,338 0.5

> 80,000 70,181 1,173,164,852 6.5 37 0.714 26 1,853,642 0.2

All commercial body type totals 18,147,256 36,982,024,815 9.4 2,491,143,761 6.7

Note: “Other” includes pickup, SUV, armored, concrete mixer, concrete pumper, crane, curtainside, low boy, pole, other service, street sweeper, tank 

(dry/bulk), tow/wrecker, vacuum, insulated non-reefer, open top, car carrier, livestock, mobile home toter, and unknown.
L. Gaines, A. Vyas, and J.L. Anderson 11

CONCLUSIONS

Extended idling by commercial trucks represents a significant use of our petroleum resources, 

and much of this oil use could be avoided by installing idle-reduction technologies, by adopting 

vehicle scheduling policies, or simply by turning the trucks off. Until now, attention has been 

focused on overnight idling by tractor-trailers with sleepers, which represent a very visible and 

obvious target for conservation and emission-reduction efforts. However, commercial trucks of 

all sizes idle for extended periods (0.5 hour or more) during their workdays, for a variety of 

reasons, such as while drivers wait to pick up or drop off a load or as a means of providing a 

warm haven for workers fixing utilities or roads in inclement weather. The quantity of petroleum 

used by such trucks may be far greater than that used by sleepers idling overnight. Although the 

length of time these vehicles idle is considerably shorter than the 6–10 hours that sleepers idle, 

the sheer number of vehicles more than makes up for it. 

The sum of overnight and workday idling of trucks may consume well over 

2 billion gallons of oil (mostly diesel) annually in the United States. To develop an accurate 

estimate of idling fuel use, data on vehicles and fleets in many industries would have to be 

collected. Cost-effective technologies exist for reducing overnight idling, but the fewer hours 

trucks idle per day while working will be somewhat of a barrier to their use in non-sleepers, 

because the payback period will be longer than the two years that the trucking industry requires. 

Further, for those vehicles that idle in queues (creep mode), some technology development will 

be required to enable slow vehicle motion without the use of the main engine. One possibility is 

use of the auxiliary power unit to supply minimal motive power. It will be a challenge to extend 

the realm of idle-reduction technologies to solve the problem of workday idling.

ACKNOWLEDGMENTS

The authors would like to thank the Office of FreedomCAR and Vehicle Technologies at the 

U.S. Department of Energy for its continued support. Argonne is operated by the University of 

Chicago under Contract W-31-109-Eng-38, for the U.S. Department of Energy.

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L. Gaines, A. Vyas, and J.L. Anderson 12

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