Transportation engineering is a branch of civil engineering that is involved in the planning, design,
operation, and maintenance of safe and efficient transportation systems. These systems include
roadways, railways, waterways, and intermodal operations. Typically, the demand is the amount
of traffic (people, cars, railcars, barges) that is expected to use a particular transportation facility,
while the supply is the quantity and type of infrastructure components (roadways, bridges,
pavements, etc.). These systems are typically large and expensive.
There are a number of attributes of transportation engineering that affect the types of statistical
theory that are used in the profession. One important aspect of transportation engineering is that
the transportation engineer is not only interested in the infrastructure (e.g., bridges, rails, etc.) and
the individual units (cars, trucks, railcars) that use the infrastructure, but also the user. Often it is
necessary to understand the interaction of all three of these entities—infrastructure, individual
units, and user—to understand the system as a whole. Typically the infrastructure and units are
considered the supply side of the equation, while the users are identified with demand.
Experimental studies, or designed experiments, are the mainstay of many standard statistics books.
They are used extensively in many engineering disciplines, including pavement engineering, that
are not necessarily applicable to transportation systems engineering. For example, consider an
engineer who is interested in the various factors that affect skid resistance and the relationship to
crash rate. From an ethical standpoint, she cannot place various types of pavement surfacing on
different sections of highway, observe what types of accidents occur, and then choose the best type
of pavement based on the empirical accident results. Instead, most transportation studies are
observational in nature, and as a result, the statistics used by transportation engineers reflect this
characteristic. In addition, it is sometimes very difficult to obtain certain data from the
transportation system, so statistical techniques that can handle missing data or use a priori
knowledge are needed. Lastly, much of the data are correlated and interdependent. For example,
the travel time on a given link is often correlated to the travel time on the immediate downstream
link. Sometimes this correlation is negative: Consider, for example, a driver stopped at a traffic
signal that is red. If the signal system is coordinated properly, the driver will have a lower
probability of being stopped at the traffic signal on the next link. At other times, however, the
correlation is positive: If one link is experiencing high travel times because of excessive demand,
then other links also will experience high travel times because of the same demand. Regardless, as
this example demonstrates, the assumption that different transportation phenomena are
independent is not always valid.
this lecture provides a brief introduction to transportation engineering including a discussion of
key players processes and other aspects of transportation after today's lecture students should be
able to discuss the various activities involved in transportation engineering as well as recent trends
in transportation and they should be able to define key transportation agencies in the role that these
agencies play in the broader context of transportation engineering so to start with will provide a
brief definition of
transportation which is simply stated the movement of people and or goods from one place to
another so in transportation we're essentially trying to get persons or goods from point a to point b
in order to satisfy several competing constraints and objectives and so the process by which we
facilitate for effective transportation
is referred to as transportation
engineering now
transportation engineering is defined by
the institute of transportation
engineers or ite
as the application of technology and
1:00
scientific principles which includes
1:03
planning design operations and then
1:05
long-term maintenance and management of
1:07
these facilities
1:08
for various modes of transportation so
1:11
most of
1:12
our work in this class will focus within
1:14
the realm of highway engineering but
1:16
this would also
1:17
be broadly applicable to air
1:19
transportation rail transportation water
1:21
transportation and so forth
1:23
and regardless of the mode we are
1:25
generally as transportation engineers
1:27
trying to provide
1:28
for transport of goods and services that
1:31
a
1:31
is efficient from a time standpoint or
1:34
rapid
1:35
we'd like to get persons from point a to
1:36
point b as quickly as possible
1:38
the secondary concern there is safety so
1:41
we're trying to minimize the likelihood
1:42
of
1:42
crashes occurring and if a crash does
1:45
occur we like to mitigate its severity
1:47
and then we have a variety of
1:49
complementary concerns as well
1:51
which could include comfort from a road
1:53
user standpoint convenience and access
1:56
to transportation systems how economical
1:59
these
1:59
are from the road user standpoint and
2:01
then also looking at any potential
2:03
adverse environmental impacts and trying
2:05
to mitigate their consequences as well
2:07
so as transportation engineers we are
2:09
generally trying to simultaneously
2:11
accomplish
2:12
this wide range of goals and that's what
2:15
we'll be covering as a part of this
2:16
course
2:17
and so when we talk about transportation
2:19
engineering there are essentially
2:21
five general phases or activities
2:24
involved with transportation engineering
2:26
and so those would include
2:28
at the highest level planning activities
2:30
so from a road agency standpoint
2:32
we'd like to be able to put together an
2:33
inventory of our road network
2:36
what facilities we have available to us
2:38
and
2:39
what's included in those facilities as
2:41
well as what their condition is
2:42
so the quality of the pavement on a
2:45
roadway
2:46
how well a roadway link is performing
2:49
from an operational standpoint how many
2:51
crashes occur on that segment
2:53
and what are the status of the various
2:55
features associated with that roadway
2:57
network
2:58
and if we have a good idea of what our
3:00
system looks like currently and what
3:01
it's projected to look like moving
3:03
forward we can then use a series of
3:05
analytical models to try to project
3:08
how system performance will vary over
3:10
time and from that we can determine
3:12
where there are weaknesses or areas for
3:14
improvement in our system and then we
3:16
can plan
3:16
projects and programs accordingly so
3:19
once we've determined that a project is
3:21
necessary we would then go through some
3:23
sort of design process
3:25
and the most general example is
3:27
horizontal and vertical alignment so
3:29
designing how the curves align on a
3:31
roadway would be one example of design
3:34
and once that design has been completed
3:36
going out and then actually constructing
3:38
that facility
3:39
and so a lot of this would be covered in
3:41
complementary classes in the
3:42
construction engineering area but we'll
3:44
at least talk in generalities
3:46
about how construction fits into the
3:47
bigger picture
3:49
and then once that road is actually put
3:50
into operation
3:52
uh transportation agencies are currently
3:55
investing
3:56
extensive efforts to provide essentially
3:58
real-time monitoring
4:00
of the performance of the systems or how
4:02
well it's operating which is where the
4:03
term operations comes from so what we
4:05
see right here in this diagram these are
4:07
just snapshots from a few what we refer
4:09
to as traffic operation
4:11
centers generally dots just like the
4:14
iowa dot here in the state are providing
4:16
real-time monitoring of the freeway
4:18
network and many of the other major
4:20
arterials that are under the control
4:22
of those municipalities and road
4:24
agencies as well
4:26
and so from these traffic operation
4:28
centers we're able to collect real-time
4:30
data on traffic speeds traffic volumes
4:33
assess whether there are traffic crashes
4:35
or other incidents that are affecting
4:37
performance of road facilities and then
4:39
we can create proactive response
4:42
in the event of some sort of issues with
4:45
the road network whether that relates to
4:46
a work zone for example or a vehicle
4:48
breaking down on the side of the road
4:50
and then going beyond operations we're
4:52
also concerned with maintenance both
4:53
short-term and long-term so
4:55
long term we're talking largely about
4:57
construction projects similar to what we
4:59
had
4:59
discussed previously how frequently
5:01
roads need to be maintained what exactly
5:04
is involved in those maintenance
5:05
activities and then also shorter
5:07
duration
5:07
maintenance if we need to go out and do
5:09
some quick fixes pothole repairs things
5:11
of that nature
5:12
and so there's a wide range of different
5:14
activities that are involved in
5:15
transportation engineering and as a part
5:17
of this course will provide
5:19
some level of coverage of various phases
5:21
of these activities
5:23
and one question that arises often is
5:25
how our transportation network has
5:27
evolved
5:28
so that it's essential how it became
5:30
what it is today and so what we see
5:32
right here
5:32
this is just a schematic map that
5:35
outlines the interstate highway system
5:37
and so what you see here we've got a
5:38
series of
5:39
high-speed roadways or the interstates
5:42
which connect
5:43
large cities across the country
5:45
basically so this isn't to scale here
5:47
but this is providing us a nice
5:48
simplistic version
5:50
of each of these various interstates and
5:52
where they run to and from
5:54
and so the eisenhower interstate
5:57
system was actually the largest public
5:59
works project
6:00
in the history of the world and so this
6:02
was completed over a series of several
6:04
decades
6:05
and as you can see it connects virtually
6:07
every major city in the united states
6:09
can be accessed by
6:11
these interstate facilities and
6:13
subsequent to that we've got a
6:14
complimentary road network as well which
6:16
is referred to as the national highway
6:18
system which includes the eisenhower
6:20
interstate system
6:22
as well as any other highways of
6:23
national significance so it includes the
6:25
interstates
6:26
it includes any u.s routes and it also
6:29
includes a large number of state
6:30
maintained highways as well
6:32
so when we look at these roadways
6:34
highways are generally designed so that
6:36
they can accommodate two primary
6:38
functions and those functions
6:39
are mobility and accessibility so you
6:41
can look at any type of road and assess
6:44
its mobility which is measuring
6:46
its ability to provide continuous high
6:49
speed travel so people would be able
6:51
to travel on a road that has high
6:53
mobility because they can move
6:55
quickly with minimum time from one
6:56
location to another but
6:58
in combination with that our road system
7:00
also needs to provide for access
7:02
so accessibility refers to the roadways
7:05
ability to actually get you to your
7:07
destination endpoint for example so a
7:09
parking lot
7:10
or the driveway to your house and if we
7:13
look at different types of road
7:15
facilities
7:16
interstates for example would provide
7:18
very high levels of mobility
7:19
can travel as fast as you would like up
7:22
to a practical upper limit
7:23
but very low access you can't get into
7:26
your driveway directly from an
7:27
interstate for example
7:29
whereas lower class facilities like your
7:31
local street network will have very good
7:32
access you can get door-to-door
7:34
but speeds and mobility as a function of
7:37
that are much much lower and so
7:39
as you see in the diagram right here
7:40
there's a clear trade-off between
7:42
mobility and access and will operate
7:44
different types of facilities so that
7:46
they're either
7:46
primarily satisfying mobility versus
7:49
accessibility versus a combination of
7:51
the two as we'll cover
7:52
in a few of our subsequent lectures this
7:54
slide demonstrates recent trends in
7:56
passenger vehicle traffic
7:58
so what we see here this is inter-city
8:00
passenger traffic so going from one city
8:02
to another long distance travel
8:04
essentially
8:05
and what we see on the y-axis here is
8:07
the number of passenger miles traveled
8:10
in millions across the united states
8:12
going back to the 1960s and we see how
8:15
that mode
8:15
share has changed with respect to
8:18
highway versus air
8:19
versus rail versus transit and
8:22
unsurprisingly we've seen relatively
8:24
stable and low levels of utilization of
8:26
transit and the rail system
8:28
we've seen significant increases in air
8:31
traffic over the past 40 to 50 years but
8:33
they haven't
8:34
been nearly that of what we've seen in
8:36
the highway network so
8:37
now we see virtually every household in
8:40
america has an automobile and we had
8:42
seen
8:42
a period of nearly consistent linear
8:45
growth from the 60s up through roughly
8:47
2000
8:48
now subsequently over the last 10 years
8:50
that traffic is leveled off as you can
8:52
see right here
8:54
but this drastic growth that we've
8:56
experienced over time has had a number
8:58
of
8:58
repercussions that we're feeling with
9:00
respect to operation of this
9:02
transportation network
9:03
if we look at the freight side of things
9:05
so the prior slide demonstrated the
9:08
movement of persons over long distance
9:10
this is
9:10
demonstrating freight movement and
9:12
somewhat surprisingly perhaps you'll
9:13
notice here that the largest share of
9:15
freight traffic is actually using a rail
9:18
system
9:19
and the primary reason for that is that
9:20
the rail system is relatively low cost
9:23
to operate and ship particularly for
9:26
very large pieces of cargo
9:28
we've seen significant increases in the
9:31
share of truck traffic so this would be
9:33
large commercial vehicles or semi trucks
9:35
you would see on the interstate system
9:37
for example
9:38
and we've seen drops in transport by
9:41
water
9:41
and less transport by air as well a lot
9:44
of that relates to cost and
9:45
accessibility issues for those
9:47
respective
9:48
types of facilities so looking at large
9:51
scale trends and travel what we see
9:53
right here
9:54
this is just showing us the relative
9:56
ratio if we compare
9:58
at five year increments back to a
9:59
baseline of 1980
10:01
this is vehicle miles of travel so how
10:03
much traffic is generated
10:05
nationally versus the number of lane
10:07
miles that are present in a
10:08
transportation system and so what you
10:10
see if you go back
10:11
over the last 30 to 40 years is traffic
10:14
has been
10:15
increasing at a very rapid rate but our
10:18
road infrastructure has remained
10:20
relatively stable and you've probably
10:21
noticed we're not constructing a lot of
10:23
new roads and so consequently
10:25
we have a system that's largely built up
10:28
but this increase in traffic volume has
10:30
made it congested and introduced the
10:32
number of maintenance concerns which
10:34
we're now trying to deal with and so
10:36
the fully built system is just under a
10:38
million miles in some total and then
10:41
includes a 45 000 mile interstate system
10:44
as well as 161 000 miles for our
10:47
national highway system which includes
10:49
those higher class facilities i had
10:50
alluded to previously and so
10:52
each of these highways is subject to a
10:55
number of
10:56
important transportation related
10:58
concerns as we'll detail on the next
11:00
slide so those three primary areas that
11:02
comprise many of our
11:04
current transportation challenges are
11:06
congestion safety and infrastructure
11:08
so congestion we're essentially looking
11:10
at the effects of adding
11:11
a large number of cars to our road
11:13
facilities and so if we look at some
11:15
total there are roughly 314 million
11:18
people in the united states and with
11:20
that we have 253 million automobiles
11:22
approximately
11:23
and if we try to account for the costs
11:26
in terms of
11:27
lost productivity and the other
11:29
operation and maintenance costs
11:31
associated with this congestion
11:33
the monetary value of the economic
11:35
losses due to congestion amount to
11:37
roughly 121 billion dollars annually
11:40
which is actually very small in
11:41
comparison to the safety costs
11:43
if we look nationally we've been
11:45
averaging anywhere between 30 and 35 000
11:48
traffic fatalities each year in the
11:50
united states over the past decade or so
11:52
and an additional 2 million injuries and
11:55
if we account for the costs of these
11:56
crashes
11:57
those add up to a staggering 300 billion
12:00
dollars annually so just looking at
12:02
operational and safety concerns
12:04
that comes close to a half trillion
12:06
dollars and that's before we consider
12:08
the actual infrastructure costs
12:10
and if we look at the quality of our
12:12
transportation system there's been much
12:14
publicity recently
12:16
the american society of civil engineers
12:18
issues an infrastructure report card and
12:20
it's been well publicized that our
12:22
infrastructure and its totality received
12:24
a grade of d plus during the most recent
12:26
evaluation and as you'll see here
12:28
our roads were given a grade of d and in
12:31
sum total
12:32
to improve the entire american
12:34
infrastructure by 2020 would require 3.6
12:37
trillion dollars
12:38
now with roads being a portion of that
12:40
but quite a large portion if we look
12:42
nationally
12:43
and a question that arises in us how do
12:45
we actually pay for these
12:47
improvements to our transportation
12:48
system and historically the answer to
12:51
that question has been the gasoline tax
12:52
so i'm sure many of you are familiar
12:54
anytime you go to the gas pump
12:56
you're paying 18.4 cents per gallon for
12:59
the federal gas tax
13:00
and then each state is also going to
13:02
implement their own
13:04
state-specific gas tax which is then
13:06
used to help provide additional
13:07
supplementary funding the states for
13:09
transportation improvements
13:11
and so those state taxes range from 11
13:13
cents in alaska to a high of nearly 60
13:16
cents in connecticut
13:17
and within the past 12 months there's
13:18
been a lot of discussion in iowa and we
13:20
recently had our first increase in
13:22
several decades
13:23
to a state gas tax at 32 cents per
13:26
gallon
13:26
which is right around in line with the
13:28
state average across the united states
13:30
here
13:31
and so just for a bit of a sense of
13:33
scale here that 10 cent
13:35
increase is going to generate roughly an
13:37
additional 215 million dollars
13:39
per year and so our challenge moving
13:42
forward
13:43
is really to be able to sustain this
13:45
level of funding because the gas tax
13:48
is running into a rather severe
13:50
practical issue
13:52
in that vehicles are now being designed
13:53
to be more fuel efficient than ever
13:55
before
13:56
and what the result of that is if
13:57
vehicles are more fuel efficient
13:59
we're not generating as much gas tax and
14:01
so this is
14:03
ultimately not a sustainable long-term
14:05
enterprise and so we're looking at other
14:07
ways to try to improve this
14:09
and to raise additional monies another
14:11
concern that comes into play here is
14:13
that these taxes are not actually
14:15
indexed to inflation so iowa had been at
14:17
a 22 cent gas tax
14:19
for several decades and since that
14:22
wasn't accounting for the effects of
14:23
inflation
14:24
we're actually getting less bang for the
14:26
buck over time and so the combination
14:29
of the fact that it's not indexed for
14:30
inflation and
14:32
gasoline consumption is going down have
14:34
created a real
14:35
a real funding issue that currently a
14:37
number of states are looking at creative
14:39
ways to try to rebuild that base
14:41
and so looking at who expends these
14:44
funds and who is
14:45
building this transportation network
14:47
we'll just wrap up with a quick
14:48
introduction
14:49
to a few of the key transportation
14:51
agencies so when we talk about
14:52
transportation
14:53
everything essentially runs through the
14:55
united states department of
14:56
transportation so this
14:58
is actually a cabinet-level branch of
14:59
the us government
15:01
which means we have a secretary for
15:02
transportation who oversees all aspects
15:05
of the usdot
15:06
and the usdot is then serving as an
15:08
umbrella organization for a dozen
15:10
additional agencies under its
15:12
jurisdiction which would include
15:14
the faa the federal aviation
15:16
administration who's responsible for air
15:18
traffic
15:18
and that would include everything from
15:20
air traffic control to security to the
15:22
transport of
15:24
cargo or passengers across the united
15:26
states
15:27
the highway network is under the
15:28
jurisdiction of the federal highway
15:30
administration so the fhwa
15:32
serves several functions but among the
15:34
most important of those
15:36
are allocating transportation funding
15:38
and then also providing maintenance over
15:40
any
15:41
federally maintained highway facilities
15:43
the fmcsa
15:45
or federal motor carrier safety
15:46
administration is concerned with
15:48
large truck traffic so looking at
15:50
commercial vehicles and semi trucks
15:52
and there are very stringent guidelines
15:54
in terms of the condition of those
15:56
vehicles
15:57
as well as driver regulations in terms
15:59
of how frequently
16:01
a person is able to drive and for how
16:03
long and so those are a few of the
16:04
things that fall under fmcsa
16:06
the fra federal railroad administration
16:09
is concerned with all
16:10
rail related transport and this is
16:12
becoming a
16:13
larger issue in light of some
16:15
initiatives where we're looking
16:16
at high-speed rapid transit being
16:19
implemented across the country the
16:21
federal transit administration would
16:23
deal with large-scale
16:24
transit systems such as subways light
16:27
rail transit systems
16:29
as well as simple bus systems and
16:32
dial-a-ride there's a wide variety of
16:34
different transit alternatives that are
16:35
available
16:36
in nitsa the national highway traffic
16:38
safety administration
16:40
is focused exclusively on automobile
16:43
safety
16:43
although the fhwa and some of the other
16:46
partner organizations are focused more
16:48
on the infrastructure
16:50
side nitsa is more behaviorally focused
16:53
so looking at things like speeding
16:55
drinking and driving seat belt use for
16:57
example beyond
17:06
of representatives from federal and
17:08
state transportation agencies
17:09
consultants
17:11
essentially anyone who would be involved
17:13
in transportation
17:14
and what ashto does is they provide high
17:17
level guidance
17:18
for issues of importance to the country
17:20
really so that we have consistent design
17:22
standards for example
17:24
with respect to the geometric design of
17:26
highways or to pavement design
17:28
so ash2 will be involved in developing
17:30
guideline documents
17:32
for example trb is also
17:35
an organization that's providing
17:38
national direction on these types of
17:39
issues so the transportation research
17:41
board
17:42
essentially establishes short-term and
17:44
long-term
17:45
directives for research that's aimed in
17:48
improving
17:48
transportation policy and practice
17:50
making transport
17:52
safer more efficient more economical and
17:54
so forth
17:55
ntsb the national transportation safety
17:58
board so in contrast to nitsa
18:00
the ntsb is concerned with large-scale
18:03
transportation disasters and accidents
18:05
so if there's an airline crash
18:08
if there's a bus crash and in these
18:10
types of events
18:11
it's possible that some of the other
18:14
transportation agencies that fall under
18:16
the usdot could be found liable
18:18
so the ntsb is actually a completely
18:20
independent third party that would
18:22
investigate the causal factors that
18:24
contribute to various large-scale
18:26
transportation disasters
18:27
and then bringing this back home to iowa
18:29
so the organizations we've talked to
18:30
prior to this have all been essentially
18:32
federal in nature
18:33
here in the state the iowa dot is
18:36
responsible for
18:37
planning construction operation of our
18:39
highway facilities
18:40
and they work in partnership with the
18:42
iowa state patrol
18:43
as well as the iowa department of public
18:46
safety
18:46
so the state patrol of course is
18:48
concerned with enforcing traffic
18:50
regulations including speed limits
18:52
drinking and driving seat belt laws
18:55
while the department
18:56
of public safety is largely looking at
18:59
evaluating the performance of the
19:01
transportation network in terms of
19:03
impacts on crashes injuries and
19:05
fatalities and so as we go through this
19:07
course we'll get a
19:08
closer introduction to a number of these
19:10
agencies and how they're involved with
19:12
the various processes
19:14
and transportation objectives we had
19:16
talked to up to this point