DATA-COLLECTION Transportation Engineering

 Page 1


CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
Chapter 6
Data Collection
6.1 Overview
The four-stage modeling, an important tool for forecasting future demand and performance of a transportation
system, was developed for evaluating large-scale infrastructure projects. Therefore, the four-stage modeling is
less suitable for the management and control of existing software. Since these models are applied to large systems,
they require information about travelers of the area in
uenced by the system. Here the data requirement is very
high, and may take years for the data collection, data analysis, and model development. In addition, meticulous
planning and systematic approach are needed for accurate data collection and processing. This chapter covers
three important aspects of data collection, namely, survey design, household data collection, and data analysis.
Finally, a brief discussion of other important surveys is also presented.
6.2 Survey design
Designing the data collection survey for the transportation projects is not easy. It requires considerable experi-
ence, skill, and a sound understanding of the study area. It is also important to know the purpose of the study
and details of the modeling approaches, since data requirement is in
uenced by these. Further, many practical
considerations like availability of time and money also has a strong bearing on the survey design. In this section,
we will discuss the basic information required from a data collection, dening the study area, dividing the area
into zones, and transport network characteristics.
6.2.1 Information needed
Typical information required from the data collection can be grouped into four categories, enumerated as below.
1. Socio-economic data: Information regarding the socio-economic characteristics of the study area.
Important ones include income, vehicle ownership, family size, etc. This information is essential in building
trip generation and modal split models.
2. Travel surveys: Origin-destination travel survey at households and trac data from cordon lines
and screen lines (dened later). Former data include the number of trips made by each member of the
household, the direction of travel, destination, the cost of the travel, etc. The latter include the trac

ow, speed, and travel time measurements. These data will be used primarily for the calibration of the
models, especially the trip distribution models.
Introduction to Transportation Engineering 6.1 Tom V. Mathew and K V Krishna Rao
Page 2


CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
Chapter 6
Data Collection
6.1 Overview
The four-stage modeling, an important tool for forecasting future demand and performance of a transportation
system, was developed for evaluating large-scale infrastructure projects. Therefore, the four-stage modeling is
less suitable for the management and control of existing software. Since these models are applied to large systems,
they require information about travelers of the area in
uenced by the system. Here the data requirement is very
high, and may take years for the data collection, data analysis, and model development. In addition, meticulous
planning and systematic approach are needed for accurate data collection and processing. This chapter covers
three important aspects of data collection, namely, survey design, household data collection, and data analysis.
Finally, a brief discussion of other important surveys is also presented.
6.2 Survey design
Designing the data collection survey for the transportation projects is not easy. It requires considerable experi-
ence, skill, and a sound understanding of the study area. It is also important to know the purpose of the study
and details of the modeling approaches, since data requirement is in
uenced by these. Further, many practical
considerations like availability of time and money also has a strong bearing on the survey design. In this section,
we will discuss the basic information required from a data collection, dening the study area, dividing the area
into zones, and transport network characteristics.
6.2.1 Information needed
Typical information required from the data collection can be grouped into four categories, enumerated as below.
1. Socio-economic data: Information regarding the socio-economic characteristics of the study area.
Important ones include income, vehicle ownership, family size, etc. This information is essential in building
trip generation and modal split models.
2. Travel surveys: Origin-destination travel survey at households and trac data from cordon lines
and screen lines (dened later). Former data include the number of trips made by each member of the
household, the direction of travel, destination, the cost of the travel, etc. The latter include the trac

ow, speed, and travel time measurements. These data will be used primarily for the calibration of the
models, especially the trip distribution models.
Introduction to Transportation Engineering 6.1 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
8
4
5
7
6
1
2
9
3
Figure 6:1: zoning of a study area
3. Land use inventory: This includes data on the housing density at residential zones, establishments at
commercial and industrial zones. This data is especially useful for trip generation models.
4. Network data: This includes data on the transport network and existing inventories. Transport network
data includes road network, trac signals, junctions etc. The service inventories include data on public
and private transport networks. These particulars are useful for the model calibration, especially for the
assignment models.
6.2.2 Study area
Once the nature of the study is identied, the study area can be dened to encompass the area of expected policy
impact. The study area need not be conrmed by political boundaries, but bounded by the area in
uenced by
the transportation systems. The boundary of the study area is dened by what is called as external cordon or
simply the cordon line. A sample of the zoning of a study area is shown in gure 6:1 Interactions with the area
outside the cordon are dened via external stations which eectively serve as doorways to trips, into, out of,
and through the study area. In short, study area should be dened such that majority of trips have their origin
and destination in the study area and should be bigger than the area-of-interest covering the transportation
project.
6.2.3 Zoning
Once the study area is dened, it is then divided into a number of small units called trac analysis zones (TAZ)
or simply zones. The zone with in the study area are called internal zones.
Zones are modeled as if all their attributes and properties were concentrated in a single point called the
zonecentroid. The centroids are connected to the nearest road junction or rail station by centroid connectors.
Both centroid and centroid connectors are notional and it is assumed that all people have same travel cost from
the centroid to the nearest transport facility which is the average for a zone. The intersection from outside
world is normally represented through external zones. The external zones are dened by the catchment area of
the major transport links feeding to the study area. Although the list is not complete, few guidelines are given
below for selecting zones.
1. zones should match other administrative divisions, particularly census zones.
2. zones should have homogeneous characteristics, especially in land use, population etc.
Introduction to Transportation Engineering 6.2 Tom V. Mathew and K V Krishna Rao
Page 3


CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
Chapter 6
Data Collection
6.1 Overview
The four-stage modeling, an important tool for forecasting future demand and performance of a transportation
system, was developed for evaluating large-scale infrastructure projects. Therefore, the four-stage modeling is
less suitable for the management and control of existing software. Since these models are applied to large systems,
they require information about travelers of the area in
uenced by the system. Here the data requirement is very
high, and may take years for the data collection, data analysis, and model development. In addition, meticulous
planning and systematic approach are needed for accurate data collection and processing. This chapter covers
three important aspects of data collection, namely, survey design, household data collection, and data analysis.
Finally, a brief discussion of other important surveys is also presented.
6.2 Survey design
Designing the data collection survey for the transportation projects is not easy. It requires considerable experi-
ence, skill, and a sound understanding of the study area. It is also important to know the purpose of the study
and details of the modeling approaches, since data requirement is in
uenced by these. Further, many practical
considerations like availability of time and money also has a strong bearing on the survey design. In this section,
we will discuss the basic information required from a data collection, dening the study area, dividing the area
into zones, and transport network characteristics.
6.2.1 Information needed
Typical information required from the data collection can be grouped into four categories, enumerated as below.
1. Socio-economic data: Information regarding the socio-economic characteristics of the study area.
Important ones include income, vehicle ownership, family size, etc. This information is essential in building
trip generation and modal split models.
2. Travel surveys: Origin-destination travel survey at households and trac data from cordon lines
and screen lines (dened later). Former data include the number of trips made by each member of the
household, the direction of travel, destination, the cost of the travel, etc. The latter include the trac

ow, speed, and travel time measurements. These data will be used primarily for the calibration of the
models, especially the trip distribution models.
Introduction to Transportation Engineering 6.1 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
8
4
5
7
6
1
2
9
3
Figure 6:1: zoning of a study area
3. Land use inventory: This includes data on the housing density at residential zones, establishments at
commercial and industrial zones. This data is especially useful for trip generation models.
4. Network data: This includes data on the transport network and existing inventories. Transport network
data includes road network, trac signals, junctions etc. The service inventories include data on public
and private transport networks. These particulars are useful for the model calibration, especially for the
assignment models.
6.2.2 Study area
Once the nature of the study is identied, the study area can be dened to encompass the area of expected policy
impact. The study area need not be conrmed by political boundaries, but bounded by the area in
uenced by
the transportation systems. The boundary of the study area is dened by what is called as external cordon or
simply the cordon line. A sample of the zoning of a study area is shown in gure 6:1 Interactions with the area
outside the cordon are dened via external stations which eectively serve as doorways to trips, into, out of,
and through the study area. In short, study area should be dened such that majority of trips have their origin
and destination in the study area and should be bigger than the area-of-interest covering the transportation
project.
6.2.3 Zoning
Once the study area is dened, it is then divided into a number of small units called trac analysis zones (TAZ)
or simply zones. The zone with in the study area are called internal zones.
Zones are modeled as if all their attributes and properties were concentrated in a single point called the
zonecentroid. The centroids are connected to the nearest road junction or rail station by centroid connectors.
Both centroid and centroid connectors are notional and it is assumed that all people have same travel cost from
the centroid to the nearest transport facility which is the average for a zone. The intersection from outside
world is normally represented through external zones. The external zones are dened by the catchment area of
the major transport links feeding to the study area. Although the list is not complete, few guidelines are given
below for selecting zones.
1. zones should match other administrative divisions, particularly census zones.
2. zones should have homogeneous characteristics, especially in land use, population etc.
Introduction to Transportation Engineering 6.2 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
3. zone boundaries should match cordon and screen lines, but should not match major roads.
4. zones should be as smaller in size as possible so that the error in aggregation caused by the assumption
that all activities are concentrated at the zone centroids is minimum.
6.2.4 Network
Transport network consists of roads,junctions, bus stops, rails, railway station etc. Normally road network and
rail network are represented separately. Road network is considered as directed graph of nodes and links. Each
node and links have their own properties. Road link is normally represented with attributes like starting node,
ending node, road length, free 
ow speed, capacity, number of lanes or road width, type of road like divided or
undivided etc. Road junctions or nodes are represented with attributes like node number, starting nodes of all
links joining the current node, type of intersection (uncontrolled, round about, signalized, etc.). Similarly public
transport network like bus transit network and rail network are represented, but with attributes relevant to
them. These may include frequency of service, fare of travel, line capacity, station capacity etc. This completes
the inventory of base-year transportation facility.
6.3 Household data
To understand the behavior and factors aecting the travel, one has got the origin of travel when the decision for
travel is made. It is where people live as family which is the household. Therefore household data is considered
to be the most basic and authentic information about the travel pattern of a city.
Ideally one should take the details of all the people in the study to get complete travel details. However,
this is not feasible due to large requirement of time and resources needed. In addition this will cause diculties
in handling these large data in modeling stage. Therefore, same sample households are randomly selected and
survey is conducted to get the household data. Higher sample size is required fro large population size, and
vice-versa. Normally minimum ten percent samples are required for population less than 50,000. But for a
population more than one million require only one percent for the same accuracy.
6.3.1 Questionnaire design
The next step in the survey is the questionnaire design. A good design will ensure better response from the
respondent and will signicantly improve the quality of data. Design of questionnaire is more of an art than
a science. However few guiding principles can be laid out. The questionnaire should be simple, direct, should
take minimum time, and should cause minimum burden to the respondent. Traditional household survey has
three major sections; household characteristics, personal characteristics, and trip details.
Household characteristics This section includes a set of questions designed to obtain socioeconomic
information about the household. Relevant questions are:number of members in the house, no.of employed
people, number of unemployed people, age and sex of the members in the house etc., number of two-wheelers
in the house, number of cycles, number of cars in the house etc., house ownership and family income.
Personal characteristics This part includes questions designed to classify the household members(older
than 5) according to the following aspects:relation to the head of the household (e.g. wife, son), sex, age,
possession of a driving license, educational level, and activity.
Trip data This part of the survey aims at detecting and characterizing all trips made by the household
members identied in the rst part. A trip is normally dened as any movement greater than 300 meters from
Introduction to Transportation Engineering 6.3 Tom V. Mathew and K V Krishna Rao
Page 4


CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
Chapter 6
Data Collection
6.1 Overview
The four-stage modeling, an important tool for forecasting future demand and performance of a transportation
system, was developed for evaluating large-scale infrastructure projects. Therefore, the four-stage modeling is
less suitable for the management and control of existing software. Since these models are applied to large systems,
they require information about travelers of the area in
uenced by the system. Here the data requirement is very
high, and may take years for the data collection, data analysis, and model development. In addition, meticulous
planning and systematic approach are needed for accurate data collection and processing. This chapter covers
three important aspects of data collection, namely, survey design, household data collection, and data analysis.
Finally, a brief discussion of other important surveys is also presented.
6.2 Survey design
Designing the data collection survey for the transportation projects is not easy. It requires considerable experi-
ence, skill, and a sound understanding of the study area. It is also important to know the purpose of the study
and details of the modeling approaches, since data requirement is in
uenced by these. Further, many practical
considerations like availability of time and money also has a strong bearing on the survey design. In this section,
we will discuss the basic information required from a data collection, dening the study area, dividing the area
into zones, and transport network characteristics.
6.2.1 Information needed
Typical information required from the data collection can be grouped into four categories, enumerated as below.
1. Socio-economic data: Information regarding the socio-economic characteristics of the study area.
Important ones include income, vehicle ownership, family size, etc. This information is essential in building
trip generation and modal split models.
2. Travel surveys: Origin-destination travel survey at households and trac data from cordon lines
and screen lines (dened later). Former data include the number of trips made by each member of the
household, the direction of travel, destination, the cost of the travel, etc. The latter include the trac

ow, speed, and travel time measurements. These data will be used primarily for the calibration of the
models, especially the trip distribution models.
Introduction to Transportation Engineering 6.1 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
8
4
5
7
6
1
2
9
3
Figure 6:1: zoning of a study area
3. Land use inventory: This includes data on the housing density at residential zones, establishments at
commercial and industrial zones. This data is especially useful for trip generation models.
4. Network data: This includes data on the transport network and existing inventories. Transport network
data includes road network, trac signals, junctions etc. The service inventories include data on public
and private transport networks. These particulars are useful for the model calibration, especially for the
assignment models.
6.2.2 Study area
Once the nature of the study is identied, the study area can be dened to encompass the area of expected policy
impact. The study area need not be conrmed by political boundaries, but bounded by the area in
uenced by
the transportation systems. The boundary of the study area is dened by what is called as external cordon or
simply the cordon line. A sample of the zoning of a study area is shown in gure 6:1 Interactions with the area
outside the cordon are dened via external stations which eectively serve as doorways to trips, into, out of,
and through the study area. In short, study area should be dened such that majority of trips have their origin
and destination in the study area and should be bigger than the area-of-interest covering the transportation
project.
6.2.3 Zoning
Once the study area is dened, it is then divided into a number of small units called trac analysis zones (TAZ)
or simply zones. The zone with in the study area are called internal zones.
Zones are modeled as if all their attributes and properties were concentrated in a single point called the
zonecentroid. The centroids are connected to the nearest road junction or rail station by centroid connectors.
Both centroid and centroid connectors are notional and it is assumed that all people have same travel cost from
the centroid to the nearest transport facility which is the average for a zone. The intersection from outside
world is normally represented through external zones. The external zones are dened by the catchment area of
the major transport links feeding to the study area. Although the list is not complete, few guidelines are given
below for selecting zones.
1. zones should match other administrative divisions, particularly census zones.
2. zones should have homogeneous characteristics, especially in land use, population etc.
Introduction to Transportation Engineering 6.2 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
3. zone boundaries should match cordon and screen lines, but should not match major roads.
4. zones should be as smaller in size as possible so that the error in aggregation caused by the assumption
that all activities are concentrated at the zone centroids is minimum.
6.2.4 Network
Transport network consists of roads,junctions, bus stops, rails, railway station etc. Normally road network and
rail network are represented separately. Road network is considered as directed graph of nodes and links. Each
node and links have their own properties. Road link is normally represented with attributes like starting node,
ending node, road length, free 
ow speed, capacity, number of lanes or road width, type of road like divided or
undivided etc. Road junctions or nodes are represented with attributes like node number, starting nodes of all
links joining the current node, type of intersection (uncontrolled, round about, signalized, etc.). Similarly public
transport network like bus transit network and rail network are represented, but with attributes relevant to
them. These may include frequency of service, fare of travel, line capacity, station capacity etc. This completes
the inventory of base-year transportation facility.
6.3 Household data
To understand the behavior and factors aecting the travel, one has got the origin of travel when the decision for
travel is made. It is where people live as family which is the household. Therefore household data is considered
to be the most basic and authentic information about the travel pattern of a city.
Ideally one should take the details of all the people in the study to get complete travel details. However,
this is not feasible due to large requirement of time and resources needed. In addition this will cause diculties
in handling these large data in modeling stage. Therefore, same sample households are randomly selected and
survey is conducted to get the household data. Higher sample size is required fro large population size, and
vice-versa. Normally minimum ten percent samples are required for population less than 50,000. But for a
population more than one million require only one percent for the same accuracy.
6.3.1 Questionnaire design
The next step in the survey is the questionnaire design. A good design will ensure better response from the
respondent and will signicantly improve the quality of data. Design of questionnaire is more of an art than
a science. However few guiding principles can be laid out. The questionnaire should be simple, direct, should
take minimum time, and should cause minimum burden to the respondent. Traditional household survey has
three major sections; household characteristics, personal characteristics, and trip details.
Household characteristics This section includes a set of questions designed to obtain socioeconomic
information about the household. Relevant questions are:number of members in the house, no.of employed
people, number of unemployed people, age and sex of the members in the house etc., number of two-wheelers
in the house, number of cycles, number of cars in the house etc., house ownership and family income.
Personal characteristics This part includes questions designed to classify the household members(older
than 5) according to the following aspects:relation to the head of the household (e.g. wife, son), sex, age,
possession of a driving license, educational level, and activity.
Trip data This part of the survey aims at detecting and characterizing all trips made by the household
members identied in the rst part. A trip is normally dened as any movement greater than 300 meters from
Introduction to Transportation Engineering 6.3 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
an origin to a destination with a given purpose. Trips are characterized on the basis of variables such as: origin
and destination, trip purpose, trip start and ending times, mode used, walking distance, public-transport line
and transfer station or bus stop (if applicable).
6.3.2 Survey administration
Once the questionnaire is ready, the next step is to conduct the actual survey with the help of enumerators.
Enumerators has to be trained rst by brieng them about the details of the survey and how to conduct the
survey. They will be given random household addresses and the questionnaire set. They have to rst get
permission to be surveyed from the household. They may select a typical working day for the survey and ask
the members of the household about the details required in the questionnaire. They may take care that each
member of the household should answer about their own travel details, except for children below 12 years. Trip
details of children below 5 years are normally ignored. Since the actual survey may take place any time during
the day, the respondents are required to answer the question about the travel details of the previous day.
There are many methods of the administration of the survey and some of them are discussed below:
1. Telephonic: The enumerator may use telephone to x an appointment and then conduct detailed
telephonic interview. This is very popular in western countries where phone penetration is very high.
2. Mail back: The enumerator drops the questionnaire to the respondent and asks them to ll the details
and mail them back with required information. Care should be taken to design the questionnaire so that
it is self explanatory.
3. Face-to-face In this method, the enumerator visits the home of the respondent and asks the questions
and lls up the questionnaire by himself. This is not a very socially acceptable method in the developed
countries, as these are treated as intrusion to privacy. However, in many developed countries, especially
with less educated people, this is the most eective method.
6.4 Data preparation
The raw data collected in the survey need to be processed before direct application in the model. This is
necessary, because of various errors, except in the survey both in the selection of sample houses as well as
error in lling details. In this section, we will discuss three aspects of data preparation; data correction, data
expansion, and data validation.
6.4.1 Data correction
Various studies have identied few important errors that need to be corrected, and are listed below.
1. Household size correction It may be possible that while choosing the random samples, one may choose
either larger or smaller than the average size of the population as observed in the census data and correction
should be made accordingly.
2. Socio-demographic corrections It is possible that there may be dierences between the distribution
of the variables sex, age, etc. between the survey, and the population as observed from the census data.
This correction is done after the household size correction.
Introduction to Transportation Engineering 6.4 Tom V. Mathew and K V Krishna Rao
Page 5


CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
Chapter 6
Data Collection
6.1 Overview
The four-stage modeling, an important tool for forecasting future demand and performance of a transportation
system, was developed for evaluating large-scale infrastructure projects. Therefore, the four-stage modeling is
less suitable for the management and control of existing software. Since these models are applied to large systems,
they require information about travelers of the area in
uenced by the system. Here the data requirement is very
high, and may take years for the data collection, data analysis, and model development. In addition, meticulous
planning and systematic approach are needed for accurate data collection and processing. This chapter covers
three important aspects of data collection, namely, survey design, household data collection, and data analysis.
Finally, a brief discussion of other important surveys is also presented.
6.2 Survey design
Designing the data collection survey for the transportation projects is not easy. It requires considerable experi-
ence, skill, and a sound understanding of the study area. It is also important to know the purpose of the study
and details of the modeling approaches, since data requirement is in
uenced by these. Further, many practical
considerations like availability of time and money also has a strong bearing on the survey design. In this section,
we will discuss the basic information required from a data collection, dening the study area, dividing the area
into zones, and transport network characteristics.
6.2.1 Information needed
Typical information required from the data collection can be grouped into four categories, enumerated as below.
1. Socio-economic data: Information regarding the socio-economic characteristics of the study area.
Important ones include income, vehicle ownership, family size, etc. This information is essential in building
trip generation and modal split models.
2. Travel surveys: Origin-destination travel survey at households and trac data from cordon lines
and screen lines (dened later). Former data include the number of trips made by each member of the
household, the direction of travel, destination, the cost of the travel, etc. The latter include the trac

ow, speed, and travel time measurements. These data will be used primarily for the calibration of the
models, especially the trip distribution models.
Introduction to Transportation Engineering 6.1 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
8
4
5
7
6
1
2
9
3
Figure 6:1: zoning of a study area
3. Land use inventory: This includes data on the housing density at residential zones, establishments at
commercial and industrial zones. This data is especially useful for trip generation models.
4. Network data: This includes data on the transport network and existing inventories. Transport network
data includes road network, trac signals, junctions etc. The service inventories include data on public
and private transport networks. These particulars are useful for the model calibration, especially for the
assignment models.
6.2.2 Study area
Once the nature of the study is identied, the study area can be dened to encompass the area of expected policy
impact. The study area need not be conrmed by political boundaries, but bounded by the area in
uenced by
the transportation systems. The boundary of the study area is dened by what is called as external cordon or
simply the cordon line. A sample of the zoning of a study area is shown in gure 6:1 Interactions with the area
outside the cordon are dened via external stations which eectively serve as doorways to trips, into, out of,
and through the study area. In short, study area should be dened such that majority of trips have their origin
and destination in the study area and should be bigger than the area-of-interest covering the transportation
project.
6.2.3 Zoning
Once the study area is dened, it is then divided into a number of small units called trac analysis zones (TAZ)
or simply zones. The zone with in the study area are called internal zones.
Zones are modeled as if all their attributes and properties were concentrated in a single point called the
zonecentroid. The centroids are connected to the nearest road junction or rail station by centroid connectors.
Both centroid and centroid connectors are notional and it is assumed that all people have same travel cost from
the centroid to the nearest transport facility which is the average for a zone. The intersection from outside
world is normally represented through external zones. The external zones are dened by the catchment area of
the major transport links feeding to the study area. Although the list is not complete, few guidelines are given
below for selecting zones.
1. zones should match other administrative divisions, particularly census zones.
2. zones should have homogeneous characteristics, especially in land use, population etc.
Introduction to Transportation Engineering 6.2 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
3. zone boundaries should match cordon and screen lines, but should not match major roads.
4. zones should be as smaller in size as possible so that the error in aggregation caused by the assumption
that all activities are concentrated at the zone centroids is minimum.
6.2.4 Network
Transport network consists of roads,junctions, bus stops, rails, railway station etc. Normally road network and
rail network are represented separately. Road network is considered as directed graph of nodes and links. Each
node and links have their own properties. Road link is normally represented with attributes like starting node,
ending node, road length, free 
ow speed, capacity, number of lanes or road width, type of road like divided or
undivided etc. Road junctions or nodes are represented with attributes like node number, starting nodes of all
links joining the current node, type of intersection (uncontrolled, round about, signalized, etc.). Similarly public
transport network like bus transit network and rail network are represented, but with attributes relevant to
them. These may include frequency of service, fare of travel, line capacity, station capacity etc. This completes
the inventory of base-year transportation facility.
6.3 Household data
To understand the behavior and factors aecting the travel, one has got the origin of travel when the decision for
travel is made. It is where people live as family which is the household. Therefore household data is considered
to be the most basic and authentic information about the travel pattern of a city.
Ideally one should take the details of all the people in the study to get complete travel details. However,
this is not feasible due to large requirement of time and resources needed. In addition this will cause diculties
in handling these large data in modeling stage. Therefore, same sample households are randomly selected and
survey is conducted to get the household data. Higher sample size is required fro large population size, and
vice-versa. Normally minimum ten percent samples are required for population less than 50,000. But for a
population more than one million require only one percent for the same accuracy.
6.3.1 Questionnaire design
The next step in the survey is the questionnaire design. A good design will ensure better response from the
respondent and will signicantly improve the quality of data. Design of questionnaire is more of an art than
a science. However few guiding principles can be laid out. The questionnaire should be simple, direct, should
take minimum time, and should cause minimum burden to the respondent. Traditional household survey has
three major sections; household characteristics, personal characteristics, and trip details.
Household characteristics This section includes a set of questions designed to obtain socioeconomic
information about the household. Relevant questions are:number of members in the house, no.of employed
people, number of unemployed people, age and sex of the members in the house etc., number of two-wheelers
in the house, number of cycles, number of cars in the house etc., house ownership and family income.
Personal characteristics This part includes questions designed to classify the household members(older
than 5) according to the following aspects:relation to the head of the household (e.g. wife, son), sex, age,
possession of a driving license, educational level, and activity.
Trip data This part of the survey aims at detecting and characterizing all trips made by the household
members identied in the rst part. A trip is normally dened as any movement greater than 300 meters from
Introduction to Transportation Engineering 6.3 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
an origin to a destination with a given purpose. Trips are characterized on the basis of variables such as: origin
and destination, trip purpose, trip start and ending times, mode used, walking distance, public-transport line
and transfer station or bus stop (if applicable).
6.3.2 Survey administration
Once the questionnaire is ready, the next step is to conduct the actual survey with the help of enumerators.
Enumerators has to be trained rst by brieng them about the details of the survey and how to conduct the
survey. They will be given random household addresses and the questionnaire set. They have to rst get
permission to be surveyed from the household. They may select a typical working day for the survey and ask
the members of the household about the details required in the questionnaire. They may take care that each
member of the household should answer about their own travel details, except for children below 12 years. Trip
details of children below 5 years are normally ignored. Since the actual survey may take place any time during
the day, the respondents are required to answer the question about the travel details of the previous day.
There are many methods of the administration of the survey and some of them are discussed below:
1. Telephonic: The enumerator may use telephone to x an appointment and then conduct detailed
telephonic interview. This is very popular in western countries where phone penetration is very high.
2. Mail back: The enumerator drops the questionnaire to the respondent and asks them to ll the details
and mail them back with required information. Care should be taken to design the questionnaire so that
it is self explanatory.
3. Face-to-face In this method, the enumerator visits the home of the respondent and asks the questions
and lls up the questionnaire by himself. This is not a very socially acceptable method in the developed
countries, as these are treated as intrusion to privacy. However, in many developed countries, especially
with less educated people, this is the most eective method.
6.4 Data preparation
The raw data collected in the survey need to be processed before direct application in the model. This is
necessary, because of various errors, except in the survey both in the selection of sample houses as well as
error in lling details. In this section, we will discuss three aspects of data preparation; data correction, data
expansion, and data validation.
6.4.1 Data correction
Various studies have identied few important errors that need to be corrected, and are listed below.
1. Household size correction It may be possible that while choosing the random samples, one may choose
either larger or smaller than the average size of the population as observed in the census data and correction
should be made accordingly.
2. Socio-demographic corrections It is possible that there may be dierences between the distribution
of the variables sex, age, etc. between the survey, and the population as observed from the census data.
This correction is done after the household size correction.
Introduction to Transportation Engineering 6.4 Tom V. Mathew and K V Krishna Rao
CHAPTER 6. DATA COLLECTION NPTEL May 3, 2007
3. Non-response correction It is possible that there may not be a response from many respondents,
possible because they are on travel everyday. Corrections should be made to accommodate this, after the
previous two corrections.
4. Non-reported trip correction In many surveys people underestimate the non-mandatory trips and the
actual trips will be much higher than the reported ones. Appropriate correction need to be applied for
this.
6.4.2 Sample expansion
The second step in the data preparation is to amplify the survey data in order to represent the total population
of the zone. This is done with the help of expansion factor which is dened as the ratio of the total number
of household addressed in the population to that of the surveyed. A simple expansion factor F
i
for the zone i
could be of the following form.
F
i
=
a
b d
(6.1)
where a is the total number of household in the original population list, b is the total number of addresses
selected as the original sample, and d is the number of samples where no response was obtained.
6.4.3 Validation of results
In order to have condence on the data collected from a sample population, three validation tests are adopted
usually. The rst simply considers the consistency of the data by a eld visit normally done after data entry
stage. The second validation is done by choosing a computational check of the variables. For example, if age of
a person is shown some high unrealistic values like 150 years. The last is a logical check done for the internal
consistency of the data. For example, if the age of a person is less than 18 years, then he cannot have a driving
license. Once these corrections are done, the data is ready to be used in modeling.
6.5 Other surveys
In addition to the household surveys, these other surveys are needed for complete modeling involving four stage
models. Their primary use is for the calibration and validation of the models, or act as complementary to the
household survey. These include O-D surveys, road side interviews, and cordon and screen line counts.
6.5.1 O-D survey
Sometime four small studies, or to get a feel of the O-D pattern without doing elaborate survey, work space
interviews are conducted to nd the origin-destination of employers in a location. Although they are biased in
terms of the destination, they are random in terms of the mode of travel.
6.5.2 Road side interviews
These provide trips not registered in a household survey, especially external-internal trips. This involves asking
questions to a sample of drivers and passengers of vehicles crossing a particular location. Unlike household
survey, the respondent will be asked with few questions like origin, destination, and trip purpose. Other
Introduction to Transportation Engineering 6.5 Tom V. Mathew and K V Krishna Rao