LDTP 78-13
Draft Technical Report
The Amount of Vehicle Operation
over 50 MPH
July 1978
by
Myriam Torres
Notire
Technical He-ports do not necessarily represent final EPA decisions or
pc.si tioi:r.. They are intended to present technical analysis of issues
using data which are currently available. The purpose in the release of
such reports is to facilitate the exchange of technical information and
to inform the public of technical developments vhich may form the basis
for a final EPA det.ision, position or regulatory actiom
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
U.S. Environmental Protection Agency
-------
I. Introduction
It is a well known fact that vehicle operational characteristics, in
particular vehicle driving speeds, are one of the factors that affect a
vehicle's fuel economy. It has been found that as a1vehicle's speed
increases beyond 45 rcph, its fuel econoay decreases.* The purpose of
this report is to combine and present all existing public information on
the amount of vehicle operation at speeds greater than 50 aph. An
extensive data search was conducted to gather information on the aaount
of ir.iles travelled and time spent in these high speeds. These amounts
are then compared to the same parameters calculated from the EPA dynamometer
driving schedules.
II. Data Presentation
Three primary sources were used for gathering the vehicle speed information.
These sources were: the Federal Highway Administration's Highway Statistics
for 1974 and 1975; Scott Research Laboratories' Vehicle Operations Survey;
and General Motor's Chase Car Survey. A summary of the data from each
nource is presented in the following sections.
A. Fedeval Highway Administration (FliwA)
The FHv\.gathers its vehicle miles travelled and speed data from State
highway departments. Therefore, the information presented in this
section is based on statistics summarized for nost states and in some
cases for all the s-tates in the nation. Tables 1 and 2 correspond to
Table VS-1 from the 1974 and 1975 Highway Statistics . Notice in parti-
cular the column that is heavily outlined. This column gives the percent
of passenger cars exceeding 50 nph when the traffic is free-floving,
that is, the only obstacle for reducing their speed is the speed limit.
If these percentages are weighed by the percent of Vehicle Miles Travelled
(VMT) on these roads, we can then obtain a weighted average of the
percent of vehicles exceeding 50 mph for the urban and rural roads, and
for the U.S. total for free-flowing traffic. The weights were derived
using the information in Tables 3 and 4 that correspond to the Highway
Statistics'- Table VM-2 for 1974 and 1975. These data and the computations
performed for estimating the weighted averages can be found in Table 5.
The averages are highlighted by a square box. These estimated averages
do not include data for all the different FHwA road classifications
since not all the road categories in Table VS-1 are the same categories
that are found in Table VM-2. However, all the principal heavily travelled
roads are included and these roads account for tcore than half of the
total United States road mileage. In addition, the fact that not all
the roads were included in the analysis is not likely to affect the
calculated averages significantly since some roads left out were high
speed roads and some were low speed roads. Therefore their effec.t on
the average should cancel each other out. The road types that are not
considered for the calculations are marked with an X on Tables 1 to 4.
-------
Table 1
AVERAGE SPEEDS AND PERCENTAGES OF FREE-MOVING VEHICLES EXCEEDING VARIOUS SPEEDS.
BY TYPE OF HIGHWAY - 1974'
>»
rf»
1IHI 1
;x
«,
l»»| »J,»
>
I0« t>J
1*4 »J» It* 13*
t« «.».-.
10* la*
1C* 1** |»* t^*
<> «.».".
100 (»0
n i«t n ix
»T
J_J
*V
t*
t|
*.«.
.
« IW
'
\\ *.r.H.
! ?J
M ** If IX
»f ^.r.M.
u ;»
ti *| « ft
kt I.'.H.
It--
J» 1* II tt
H «.r.f.
«
It 11 * f
>U KM* lltlllMI O<
It .».«.
I
« I 1 *
£
o
4 tvl
3- I
-------
AVERAGE SPEEDS AND PERCENTAGES OF FREE-MOVING VEHICLES EXCEEDING VARIOUS SPEFDS,
BY TYPE OF HIGHWAY - 1975
Table 2
Reproduced from
bcsl available copy.
l«*l
"^>iC
^^
)
">
-><
V
V*« **l*«**l|tl/l, .......I.*..
tt.t it. 1 >». t U./
»*,» >». t » i.» K. 1
l>1 l« l«* 101
i ia IM t «
IM I»S 190 l»4
« «> « *
* t 1 VI It 1 M
U
11
it It
fj IJ
t <1 ft »|
»t 1* * *l
M II i* 1'
it 1 1 t 1 It
'
i r * i
t* t« f t*
i t »
iii*
till
lit*
i t
Source: U.S. Federal Highway Administration, Hi&hway Statistics, 1975.
-------
VEHICLE MILES, BY STATE AND HIGHWAY SYSTEM-1974
Tnblo 3
ratn )
**»* .<*
I.Ml
!.»>
(.IS
l.ffc
ITt
UT
iM
1.-**
i.ns
j^>
u*
I.P.T
tM
1.1"
I.C-*
V*
».>*»
.
i.tn
I.1M
» ttA
X
fa
M
1,1*
ur
/.no
!-sl
: >»*
'.*'*
r.arr
I.1U
1..!^
tlui
».*»'
).*»
\.\ft
l.ffl/
i.r*
i^»*
l.U*
.| ..~
*,»M
1.H1
1.*^
l.tSI
I.Jlf
X
11.1)1
l.fJ
IT*
1,1'-*
.£
T.I*
IC.'W
*.t>J
IJ.W7
>.!'*
J.fv«
».r,o
l.vn
ft.tr>
l.»o?
f .lot
*>,'*
I!MI
ITT. in
i.r.T
l.rr
i.tWt
.
M*
l,v'^
11
l>1t
.
>-*
I.tM
).»!
It.VO
9»\
in
Vt
n»
i.ni
«.»
I/'S"
Jl
!«.»«
~77*r
'.»'.»
lt.«T7
^.*)
1..V.*
.
if .*!»
n.fl/t
If. Ml
).*U
»,&T*
).?*
I.*.*
!>*)
f.P*
!*.!»,
n.w
».D)
p.nr
[;£,'
UKJ
^»* fsu »*«^i
!_.'. IK..,,.l, ,r.-,l^-,. ,r.U» A M R. U I»J.~J I.
I
<5'
a
-
I
O
-------
VEHICLE MILES, BY STATE AND HIGHWAY SYSTEM -1975
Table l*
- I
'.If It,
MBT» i
«n i
-«.
..«,
twrv i
W.K* t
__^_
_.
..,,,
mn M
*.
. ». t*
***.* i*
*« -
" r
r
i
f »#! !»* |
~-?~
T....I
H'-iiS--1-
*!*>*
<*-'!!
xo
*«!
*»**
»~-_..
TM4
»»*!
UWt* I/
*,.!.<<-*
t»!U
f«0 !*
** . Ill ***
.J. ^».» * »m
"*'
-r>
J"1 I
I.T-
1.."
I./-* I
*tO
"1 [
**7
. . ^
11. fT* |
I;::; !
/ .'. *
"*i" i
***
t.'fn
»*."*
»,!»
!*A
I.*' i
!-.,*«
.>
,.,~
T-S
M.
I.e**
».»*
4
l/l"
$
».\>;
lll.T1*
l».JM
*<-> {***
.. i t»ftt.
cr.-t *.*
41
I/
11
1*?
ll'
u»
,*
f"
.,- ,
'.-T ;
V*
» ^
**
il
ill
.>«
I/I
»*#
*
m
T*
I, lit
'
i
^1 *
Ml
U
ll*
M'
It!
tri
i.'ti
m
*»,
I .!-
M..-
>* .in
u 1
1
**!
"* 1
1.***
i -o
l.**.v
* . **
-.-_
V;^
*«*"
iV.I W
K*!
1.* !
I."V.
1 . *^l
*.'u»
1' . '.V
t. -».
l>*
l.>v
l.llf
».*!
U.V-*
f.'/l
11..^.
l.n-*
/.a /
^.11*
,.N.»*
-.1.1.1
~t f\r*~'
1",
" 1
'in
i. V*
-*
«,»U
Ilk
ui
*.**
_i.«_
f.-'
t».TO
!*«
..-i
ij.t
* n
!«.»»
..T.l
IT
**»
».^«
i!»-«
».**
lie .0
-*..v.
*«Z^T^t
»..> .--
17 >
u
\«
i.v
r.*/
U
K
:."
^
I, I1*
!**
01
w
rn
»i«
«,
T
in
f.
1,V*
19
lit
ft.1
V.t
IV.V4-.
r..'/T
-_-J-^
i
'l'f
t.'.ll
f. *
T.PI
tx
»*t
I.*.".
I.W'Jl
» ^
"
ii
». »'i
t.j")
4 1
1.***
Uo
ic INI
M.-**
»*
I-A
..^»
IT
»,5!
.)>->
i.n*
l.*r.
1.1 1*
III. Ml,
:*-.iW
.!!« M
>.<(*.
fWIt
t.**
11. VI
l.l-t
W.rw
vc
T.irt
M.HI
».*»)
«.<-«
it. MI
r.i-n
W.'*
!!-«
;,,*
M >*
f. V*
i..w
1. IT
1." -»*
l.im
M.«r
i!1**
tev.n
r'.in
Mi.W»
1 1 ^ »^
*-fi«« It
f^i
t ;
l.t'r
r*
».Uf
l.TT*
fl.l**
».!*
*!rri
V1..7.
!!>-*
t.fvf
w.r*
*. V
JjtTV
"*
t'.m
"K
11.111
!:S
«.«"
/i>,>»
^i.x,.
r. *v..
«* p«al u
.. r.,,.
«..
».!'*
":^
u.»*
^v
..*
I.It*
*. t-t
vr
U.tM
l^.^n
1.'-?.
ft)»
i.^
ill
V.'
n.M
l..^?
>.f
It-'.t.*
r,,.w
rm.:r
r--.«>
,
rru
t.ttl
l.'^f
l.-'Vl
"-,:*
I.TTt
.......
»:'-l
> \*fl
f.'.tlf
VJ ,«>4
*. ' tl
n.Mv
!.'**»
I!P/»
I.IM
*;:,'"
t ,'.fi
n.in
i.m
».'J7
:».»»i
Pi,^*
h»i.i*
*ti> *r M
.;-. r.-.«
».«*J
(^
» JO
r.t
11. IV
....
I.-"
>;,;
!;S
;;;
;«
.h*
'1 . 1 1 1
1A*
V,
i «
*.»»
vo
'*.»
I./'**
I.--*
t««,l«
IF...*
»- MB*
.f 1^-r.
T
*.
f.^
i,r-
i.-'.»
n*
^.:^'.
r*
i
'p,
t.^i
1*1';*
IW
11*
r
i.i-i
J,
|.» U
"-
ISf
»t
M
Wt.
f
1.110
ir.i.i
I
1V--.M
41
V,
1. «1
11
t . m
1 ,»!
l.n;
l.rn
ll
v^
''IT
If
..«
;jj
'V
!.
>.f1
1.1M
l.TTfl
).r*
«.»l
c.'M
...£.
-**«
»*«.
A
It
in
ri
I.IM
t
IM
**
II
!.*
."
''v
l.«l
fl
T^
l.»l
a. if
».-n
1 *>>J ft*.
~u
1 611
I'V
'r-;,
i->'i
».Tr i
f* >".»
I, V."*.
ii.«.
T .V*
II. 1^1
.1.
IN...TI
*.**T
! J
n. y.
i.m
>.nl
t«.ii«
.».»«
».
..,.,,.-
IT
!«
I'.M"
41
n.«T
m
II . Uf
t Vn
>>.M1
« fill
U.fl*
»!*>
i.in
I.-.T
i.rff
H.lWt
s
f-i
r*
t.tM
'A*
O.M1
>
»."*
lll.lt*
W.tfl
1,W.
^-.
T--
..*.!
l.'*1
» TO
f.lTO
M..M
*.«
!!.>)!
IM.11^
I * . * <
»'. n*
*.nvi
It .*M
*«.pf
1 I.'I t
""
till?
.*!)«
i.*">
i»..m
).*'*
w.iti
*«,»-4
rn.nf
.^.t-
-*.r*
t r~-i
1VMI
I.Kt
t. V*
''i?
V.KI
1.1*1
f.m
«,v
J;^J
«.»*
?!.**
IJ.U1
'.**
*.**
l.f*
11, "7«
t»!r *
""'
I.***
I-!4-*
)
n.ui
M!*>
11, MI
U.-n
if. '»u
tl.T*
I*''.*/'
Pi II*
y..>-
»',F/f
IF.'^'
1.1**
ir.r*
»!"*
i*.m
»^->M
IJUI.UI
«V P «<
7T !>
»*>TT
le
l.BIQ
M
I.C.T
--.
I.'I
>.*«
l.tll
to
.1
tt
r**»
ir
i.tw,
>, c,»
too
«i
ni
t
rr
u
t
r*
u
t*>
n
n
fcr.^r*
J».-M
P. * M
. nrrv.
no
LT(
<~>
X""S
rw
(t
r
».*.
.'-.
I?
*rn
l.«M
$*».*»
ri
.»
D
t
*»
M.y«
n.»>
-
.,f,r-
xl**
i.«i
'^4
ii. n
VT
»!*«*
T.W
c*,l»4
>*»,»*
" "»» b*^
""""
25
5/r
lO.t**-
W.V^,
I.WI
f ,KW
i).n»
".*!
».»*»
n .-»«
!*.'»
v».w
».!*»
n,*f
1t.i^»*
.«»
u.w.
».'*«
t.H*
I.W1
»».«»
1.**
tf.»«
MJM
M^»
* P
*tCt.
P*4
It. HI
k"t^
m.i»
1 Tl»
11.1*4
».*«
'1:5
J.2
lU.lta
ui!rn
rt ^iw
,!;i
f».»?t
T.l**
4,l>f
11. TT
.".**..
t fjU
U.A1*
**|4%
Wl.«
ilSi
j»
m.i«j
jn.m
~-.
*~
»!»«
M.M.
l'.««
U»J»1
I
.J=*_
ZZ-i
.'>!
«.^»
n!*r»
n!n*
»W.*»1
">U
ii, ni
""
I* .MB
in.M*
'.'?!
w.»>
>.n>^r>
'->*,>.*
3
I
Fi,
3 '
a
"^ rt
-------
T.-ibl.c 5
Estimate of the Percent of Passenger C.irs Exceeding 50 mph for Free-Flowing
Traffic by Area and Road Classification for 1974 and 1975
Road Type VMT*
Urban Interstate Completed
Urban Primary
Urban Secondary
Total 3i6,359
Rural Interstate Completed 104,408
Rural Interstate Travelled-Way 14,655
Rural Primary 205,734
Rural Secondary 153,824
Total
478,621
1974
X P.C.
Over Weight x
We_l£_ht 50 raph* Percent
VMT*
1975
7. P.C.
Over Weight x
50 mpti Percent
109,647
173,028
63,684
.316
. 50.0
.184
71
25
3
22.4
12.5
.6
118,225
160,120
48,744
.361
.490
.149
80
23
11
2S.9
U. 3
1.6
1.000
L.OOO
Rural
35-5
327,095
1 . (OO
68.9
496,946 l.OOn
41.8
.218
.031
.430
.321
92
78
72
48
20.1
2.4
31.0
15.4
111,972
13,168
213,436
158,370
.225
.027
.429
.319
9A
94
79
61
21.2
2.5
33.9
19.5
i
T
77.1
* Source: U.S. Federal Highway Adntinl.stratlon, MlRlwny Statistics. 1974 and 1975.
-------
Road__Tv_p_e
Urban Incerst;itc ("cmp U-tt-il 109,047
Urban Primary 173,028
Urban Si.-coiHl.iry (>3,fi84
Kural Intcrstalo romph-toil IOJ.408
Rural Interstate Tr.-ivvl Icil-U.iy 14,-'i"i.j
Rnrrsl Primary 203,7)4
Rural Sccondarv 13),824
TabU- 5 (cont)
I'.S. Total
PJJSJli
.13)
.210
.077
.127
.013
.249
. I H6
1974
:: i-.c.
.I'LJTPil
71
23
3
92
78
72
48
Total
324,980
1.000
IVr_rc:_nl
9.4
5.3
T
11-7
17.9
8.9
(34.8
VMJ
118,225
K.0,12f)
111,972
13,168
213,43(.
158,370
8J4,041
.194
.039
.ll(>
.016
.239
.192
1975
'/. I'.C.
Over Wo I fih t x
30 nph f'crccnt
50
23
11
94
94
79
61
11.5
4.5
.f>
12.8
1.3
20.5
11.7
63.1 |
i
vj
-------
-8-
Thc calculated averages for the. U.S. total found in Table 5 (54. 8X in
1974 and 63.11 in 1975) therefore indicate that for free-flowing traffic
in the United States, a significant nurober of the passenger cars travelled
af a speed greater than 50 nph during both 1974 and 1975. The large
amount of travel at these high speeds therefore is increasingly important
because of its significant impact on the nation's overall vehicle speed
pattern and primarily on its fuel economy.
Another useful piece of information that can be estimated frca Tsoies 1
th.ru 4 is the per.-.ent of urban, rural, ar.ii total U.S. VMT at speeds
greater than 50 ir.ph. These percent apes provide a nore accurate picture
of the anount of trsvel dono in excess of that speed. In order to
estimate these average percenters, applied probability statistics
computations were needed. The assumptions and modeling required to
derive the following equation ci.n he found in Reference 3.
VMT x p.(>50) + VMT, x p7(>50) + ... + VMT x p (>50)
* "
where
VMT. = Vehicle Miles travelled on road type i
p (>50) " Percent of passenger cars travelling at speeds
greater than 50 nph on road type i
For calculation of the % Urban VMT/ > 50 mph and *.' Rural VMT/ > 50 ctph, the
VMT ' s and p^'s would be those corresponding CO the urban or rural areas
only. The road classification: used were the same ones used for the
previous analysis. The resulting percentages are presented in Table 6.
The X VMT at other speeds were also cal-.ulated and are presented in
histograa forra on Figures 1 to 3.
Table 6
Percent of Vehicle Miles Travelled in
Excess of 50 mph
Area i974 19? j
Urban 35.5% 41.8%
Rural 68.8 77.0
U.S. Total 54.8 63.1
The percentages probably increased consistently for the urban and rural
area in 1975 because 1974 was the first year when the naxiniun speed
linit was reduced to 55 roph. Drivers were most probably more aware of
their speed in 1974 bec.iusc of the new adjustment. Data for 1976 is
-------
-9-
30-
20-
2:
t_^
G
/
-------
-10-
St ill not available and even if it were available the same comparisons
could not be made since the FHwA road classifications were changed fcr
that year. However, the speed trends for naiu rural highways in Figure
4 show a slight increase almost each year in the average speed driven by
passenger cars. This same trend can also be seen for the percentage of
vehicles exceeding 50 nph except for the three years before 1974. Some
of this trend car. partly be explained by vehicles having an increasing
power/we-uht ratio up until 1970. In addition, road improvements continue
to be made thereby increasing the speed limits in some roads. Therefore,
it would seen likely i:\.zt the amount of driving in excess of 50 mph
would not decrease for 1976.
A comparison can he made of these percentages to the percent of miles ,
travelled ov.rr SO mph by the Highway Dynamometer Driving Schedule (HDDS).
Fcr this schedule, 46.5% of all the speed points are over 50 mph. In
terms of distance travelled, these speed points account for 5^.0% of the
total length of the schedule. Recall that thi percentages calculated
from the FHvA statistics are for free-flowing traffic, where stops signs
and stop lights or other factors -that can cause a reduction in speed are
not accounr.ed for. The highway cycle has these sanf characteristics of
free-flowing movement, however, its amount of speed over 50 mph is
significantly less than rhe U.S. percent of VMT exceeding that speed for
1975 (63.1/0- The difference is even larger than the numerical difference
between 54.0% and 63.]% for 1975 since this last percentage, includes
free-flowing traffic within the city where the speed travelled at is
much slower than on highways outside the city.
It would be more accurate to compare the HDDS percentage to the results
for the FltwA Rural Highways. The HDDS was actually constructed by
driving an instrumented test vehicle over a variety of non-urban roads
and highways reflecting the correct proportion of vehicle operation over
four main rural road types as classified by the FHwA. It was designed
in this manner in order to complement the UDDS that, characterizes urban
driving only. Therefore, the difference between the HDDS and FHwA data
is even larger since 68.8% of the VMT in rural roads were travelled in
excess of 50 mph in 1974 and 77.02 in 1975.
Therefore, it appears that the EPA highway driving schedule doec not
include sufficient current real-world high speeds. This is in most part
due to the fact that the data used for developing the HDDS was collected
in 1974 by driving the instrumented test vehicle on rural roads in the
southeast part of Michigan and a freeway segment in northern Ohio. The
vehicle was driven hy a trained EPA employee who simulated as much as
possible the general traffic speed. In Ohio, however, the driver purposely
maintained a maximum speed of 55 mph since the freeway travelled on was
already subject to that speed limit. The intent was to develop a rural
driving schedule that reflected the anticipated nationwide 55 mph speed
limit.
-------
65
-4 AVERAGE SPEED L
, . 40
35
OUSES
PASSENGER CARS
TRUCKS
I
194243 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75
100;
[PERCENTAGE OF VEHICLES EXCEEDING so MILES PER HOUR).. ..
35
30
;IOO
194243 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 63 69 70 71 72 73 74 75
SPEED TRENDS ON MAIN RURAL HIGHWAYS BY VEHICLE TYPE
Figure 4
Source: U.S. Federal Highway Administration, Highway Statistics, 1974 and 1975.
-------
-IV
B. Scott Research Laboratories, Inc. ;
The study conducted by SRL consisted of a five-city survey of automobile
driving patterns using the chase car method. These cities were Los
Angeles, Houston, Cincinnati, Chicago, and New York City. Therefore,
their results will reflect metropolitan driving characteristics only,
including both freeway and non-freeway travel in the city.
One of SRL's approaches to reduce their large data base was to prepare
mode-matrices for each city and for the fivp-city composite. One of
these matrices, the Normalized Time in Mode Matrix, provides the percent
of vehicle operating time for 196 modes. These 196 modes result from
the matrix having that amount of cells where each cell represents a
particular mode. Table 7 is a copy of that matrix for the five-city
composite. One of the pieces of information that can be extracted from
the table is the percent of total vehicle operation time above 50 mph in
the city. ...
The matrix is a lirtle confusing on its own and thus requires some
explanation in orde) to understand how the percent is derived. All
cruises can be founa r*long the diagonal of the matrix that runs fron
upper left to lower right. If we were interested ir. the percent of tine
spent cruising at 55 mph, that percent would be found at the intersection
of an initial speed of 55 raph and final speed of 55 mph, 1.806%. The
percent of time spent cruising at speeds greater than or equal to 55 raph
would be the sum of the last three percentages on the diagonal, 6.166/..
The percent of time spent in accelerations can be found above the-cruise .
diagonal. An .acceleration from 30 mph to 55 mph vould occur .038% of
the time. The percent of time spent in accelerating to speeds greater
than or eque L to 55 mph is the sum of the percentages under the final
speeds of 5>5, 60, and 65 mph up until the figures befo-.'e the diagonal
cruises. This percent adds up to 1.97.2%. For decelerations, the procedure
i? th
-------
Table 7
COMPACTED NUKMALI/ED TOML TIME MATRIX FOR 5-ClTY COMPOSITE .
INITIAL r-INAL SPEED, MPH
SPEEUf 0 5 10 15 20 2'j 30 35 40 45 50 55 60 65
MPH '
<*>
3 0 13.060 0.582 0.559 0.668 1.025 1.891 2.631 2.314 1.321 0.501 0.140 0.052 0.018 0.010
33
$ 5 0.577 0.746 0.2H3 0.253 0.299 0.442 0.50ft 0.427 0.236 0.092 0.028 0.012 O.U06 0.002
x
= 10 0.419 0.287 0.761 0.345 0.422 0.546 0.519 0.381 0.141 0.051 0.021 0.013 0.007 O.C05
o 15 0.505 0.2C7 0.303 0.941 0.509 0.589 0.542 0.425 0.244 0.091 0.031 0.023 0.018 O.C27
g 20 0.943 0,286 0.298 0.401 1.633 0.878 0.641 0.357 0.167 0.059 0.030 0.023 0.015 0.008
PI
£ 75 1.829 0.454 0.395 0.465 0.725 3.518 1.246 0.541 0.224 0.083 0.037 0.031 0.024 0.020
n . .
30 2.419 0.488 0.441 0.471 0.560 1.136 5.463 1.220 0.354 0.119 0.040 0.038 0.022 0.024
i
35 2.142 0.394 0.349 0.3PO 0.311 0.493 1.103 5.255 0.857 0.228 0.066 0.030 0.014 0.017
40 1.267 0.204 0.158 0.182 0.152 0.193 0.318 0.775 3.450 0.483 0.145 0.063 C.028 0.019
45 0.477 0.087 0.064 0.074 0.065 0.072 0.114 0.214 0.443 2.027 0.340 0.134 0.054 0.015
50 0.160 0.026 0.031 0."22 0.027 0.034 0,C3S 0.059 0.12R 0.319 1.535 0.330 0.107 0.040
55 0.085 0.012 0.013 0.011 0.013 0.018 0.023 0.032 0.061 0.109 0.319 1.806 0.324 0.107
60 0..043 0.013 0.006 0.005 0.006 0.007 0.010 0.020 0.020 0.053 0.109 0.323 2.069 0.292
6.5 0.037 0.014 0.005 0.001 0.002 0.001 0.002 0.008 0.010 0.016 0.031 0.098 0.28* 2.291
I .
1
NORMALIZED MODE MATRIX SUMMARY
PERCENT IDLE = 13.060
PERCENT CRUISE = 31.502
- PERCENT ACCELERATION = 29.158
PERCENT DECELERATION - 26.303
U)
M
KJ
--4
« '
0>
I
-------
-u-
are over 52.5 mph. This is less than half of the estimate ftoa the SR.L
five-city composite. The big difference in the percentages could be due
in part to the fact that 26% of the total 7.486 ciles of the UDDS are
freeway miles while 32% of the total survey ciles in all five cities
were freeway travelled miles. This large difference in the freeway
percentages results fron a difference in SRL's and EPA's dafir.ition of
urban area. SRL included in their urban definition the entire metropolitan
area that comprised both the central city and the suburban areas. EPA
defined urban as a six Rile radius area fron the Central Business District.
An increase in the amount of driving outside the central city would
result in an increase in the percentage of freeway and thus high speed
travel.
C. CM Chase Car Survey
The CM Chase Car survey was conducted in 1974 in twelve major cetro-
politan areas in the United States.' Chase cars were instrumented to ..
monitor several driving parameters while following a vehicle and duplicating
its operation. The data was primarily grouped according to the different
road types travelled on, soaio of which were rural, urban, highway, and
non-highway type of roads. In this section, the amount of driving over
50 rr.ph monitored by the CM chase cars on each of these four road types
will be presented and discussed. The data will also be compared to the .
sane statistics computed from both the UDDS and the HDDS wherever this
comparison can be made. However, final conclusions must not be draim
from these comparison since an extensive EPA study revealed that for
several reasons the CM Chase Carflsurvey results were not representative - -
of the national driving pattern. '
The percentage of mi.1, es and time spent in various speed bands for the
HDDS and CM chase car d.ita are presented in Tables 8 and 9. Tables
10 and 11 compare the CM urban data with the EPA UDDS data for the same
speed bands. The percentages for speeds over 52.5 mph derived from
these tables for the EPA schedules will not correspond exactly to the
amounts reported in the previous sections. The reason for this difference
is because CM developed a computer program to evaluate the chase car
data and this same program was employed to analyze the EPA schedules.
The percentages provided in the previous sections were derived by a
simple count of the speed points over 52.5 nph divided by the total
number-of points. A more comprehensive description of the CM chase car
and EPA comparison techniques can be found in Reference 9.
Tables 8 and 9 indicate that CM monitored a larger amount of vehicle
operation over 52.5 mph than is reflected by the HDDS. The saae obser-
vation can be made from Tables 10 and .11. The percent of miles and time
spent in speeds greater than 52.5 mph for both EPA and CM are found
directly below each table.
From Figures 5 through 7 we can extract the percent of miles travelled
at speeds greater than 52.5 mph for highways, non-highways and all road .
-------
Table 8
Percentage of Miles Spent in Speed Bands
moh ± 2,5 mph 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
EPA HDDS
CM Rural RT
.05
.01
.08
.10
.10
.21
.22
.39
.24
.85
.68
L.26
1.47
2.22 '
3.54
3.34
8.11
5.71
26.41
3.59
17.72
16.08
33,02
24.68
3.37
20.08
0
9.H
0
5.37
0
1.24
Percent Miles -52.5 mph
F.PA HDDS
41.39
CM Rural RT
60.51
mph i 2.5 raph 0
10
Table r>
Percentage of Time Spent in Speed Bands
15 20 25 « 30 35 40 45 50
55
60
65
70
EPA HDDS
CM Rural RT
4.07
1.25
.51
.96
.38
1.01
.64
1.27
.51
2.07
1.14
2.46
2.16
3,62
4.57
4.65
9.02
6.97
26.43
9.33
16.26
15.68
31.64
22.06
2.67
17.13
0
6.92
0
3.79
0
.83
Percent Time >52.5 mph
EPA HDDS
J34.3 .
CM Rural RT
50.73
Source: Elwoocl Vogt, "An.ilysls of CM Chase Car Data," EPA Report.
-------
mph - 2.5 mph 0
10
Table 10
Percentage of Miles Spent In Speed Bands
15 20 25 30 35 40 45
50
55
60 65 70 75
EPA UDUS ,84 2.38 3.78 8.68 18.53 27.90 9.77 6.68 1.27 , 4.46 8.61
CM Urban RT .62 1.84 3.75 5.84 8.52 13.88 16.47 14.91 10.60 7.57 7.02
7.10
6.07 2.31 .35 .06 .01
Percent MlJ»s
EPA TODS
7.10
CM Urbnn RT
8..80
mph - 2.5 mph 0
10
Tnble 11
Percentage of Tire Spent in Speed Dands
15 20 25 :<0 35 40 45
50
55
60 65 70 75~
EPA IJDDS 24.56 6.03 5.81 9.59 16.06 20.28 5.96 3.63 .58 1.82 3.20 2.47
CM Urban ..
RT 16.79 6.01 7.34 8.18 9.38 12.51 12.59 9.91 6.32 3.95 3.31 2.62
EPA HDDS CM Urban RT [ .
.92 .13 .02
Percent Time >52.5 mph
2.47
3.69
Source: Elwood Vogt, "Analysis of GM Chase Car Data," EPA Report.
-------
-17-
25
20
i 15
2
7.5 17.5 77.5 37.5 47.5 57.5 67.5 77.5
Speed MPH
7.5 17.5 27.5 37.5 47.5 57.5 67.5 77.5
Speed MPH
Figure 5
Percent of Miles Spent in
Speed Bands-Non-Highway Driving
% miles > 52.5 mph = 6.5%
Figure 0
Percent of Miles Spent in
Speed Bands-Highway Driving
7, miles > 52.5 mph = 597.
14
12
? lli
5
° 8
c -
»
u
£ 6
4
2
0
7.5 17.5 27.5 37.547.5 575 67.5 77.5
Si.eed MPH
Figure 7
Percent of Miles Spent in Spi»ed Bands
% miles > 52.5 mph = 26%
Source: Johnson, Formenti, Gray, and Peterson, ."Measurement of Motor
Vehicle Operation Pertinent to Fuel Economy," S\E, 750003.
-------
-18-
types combined. These percentages can be found directly under each
figure. It should be noted that theae distributions and percentages are
not weighted by the fraction of national driving mileage accumulated
annually on each road type. This was one of the reasons given for
concluding that the survey's results were not representative of the
national driving pattern. The road types that fall into CM's classi-
fication of highway and non-highway are listed below:
Highway Non-Highway
Expressway Suburban Artery
Expressway-Business r^oute Rural Unpaved
Rural Highway Urban Artery
Strip Connercialisn
Surburban - No Curb
Surburban - Curb
Surburban - Unpaved
Central Business District Parking
No Parking
Urban
Shopping Center/Parking Lot
The highway road types appear to be comparable to the HDDS's road
representation. The percent of miles travelled over 52.5 nph, 59Z,
estimated from- Figure 6 for highway driving is actually very close to
the 60.5% estimated from Table 8 for rural driving. Therefore, a com-
parison of GM highway data to the HDDS also iriicates that CM monitored
more high speeds than the EPA schedule accounts for.
Conclusions
The main conclusions of this report for vehicle operation over 50 raph
are:
1. Data reported by the Federal Highway Administration (FlIwA) indicate
that for free-flowing traffic in the United States, ever half of the
passenger cars travelled at a speed greater than 50 mph in both 1974 and
1975.
2. Approximately 54.8% in 1974 and 63.1% in 1975 of the total U.S.
Vehicle Miles Travelled (V>5T) were conducted at speeds greater than 50
mph when the traffic was free-flowing.
3. The percent of VMT at speeds exceeding 50 mph for rural roads (with
free-flowing traffic) is approximately 68.8% for 1974 and 77.0% -for
1975. These percentages are significantly larger than the 54.0% for the
EPA Highway Dynamometer Driving Schedule (HDDS). Since the HDDS is
basically a free-flowing traffic cycle it appears, that the HDDS does
not include sufficient real-world, high speeds. This is due largely to
the fact that the HDDS represents rural driving in the southeastern part
-------
-19-
of Michigan and a freeway segment in. 'northern Ohio soon after the enforce-
ir.ent of the 55 raph speed litnit in Ohio. The driver flowed with the-
traffr.c when possible, and when he was not in traffic he purposely
maintained a maximum speed of 55 raph in.order to reflect, the anticipated
nationwide 55 nph speed limit.
4. The data fron> a study conducted by Scott Research Laboratories
reveals that 10% of the average urban operation time is spent in spoeds
greater than 52.5 mph. the EPA Urban Dynancmeter Driving Schedule
(UDDS), representative of Los Angeles city driving In 1969, has 3.872 of
its speed points over 52.5 raph, less than half of SRL's estimate.
5. A comparison of the CM chase car data to the UDDS and HDDS indicates
that CM monitored more high speeds than the EPA schedules account for.
-------
References
1. "Evaluation of the Representativeness of EPA K-uel Econony Estimates,"
EPA Technical Report, January 1978.
2. Highway Statistics, U.S. Department of Transportation, Federal
Highway Administration, 1974 and 1975.
3. "Vehicle Speed Distributions", U.S. Department of Transportation
Report No. PM-T-41, June 1975.
4. "Fuel Economy Tesring; Calculation and Exhaust Emissions Test
Procedures for 1977-1979 Model Year Automobiles," Federal Register,
Vol. 41, No. 177, September 10, 1976.
5. "Vehicle Operations Survey," Scott Research Laboratories, Inc.,
December 17, 1971.
6. "Control of Air Pollution from New Motor Vehicles and New Hotor
Vehicle Engines," Federal Register, Vol. 42, No. 124, June 23, 1977.
7. Johnson, T.M., Forraenti, D.L., Gray, R.F., and Peterson, W.C.,
"Measurenent of Motor Vehicle Operation Pertinent to Fuel Economy,"
Society of Automotive EnRineers, 750003, Detroit, Michigan, February
1975.
fi. Vogt, Elvood, "Analysis of CM Ch.ise Car Data," EPA Report.
9. VoRt, Elwood, W., "Comparison of the Vehicle Operational Character-
istics of the EPA highway Dynamometer Driving Schedule with the
Rural DrivinR Data Collected by the CM Chase Car Survey," EPA.
September 1975.
------- |