what even is transportation planning?
1. Collect information on performance
2. Identify existing and forecast future system performance levels
3. Identify solutions
In other words… focus on meeting the existing and forcasted travel demand
where does planning fit in??
| Stage | Description of Activity |
|---|---|
| Planning | State DOTs, MPOs, & local gov’ts identify transportion needs; financial constraints need to be considered |
| Project Development | Transportation project is more clearly defined |
| Design | Design teams makes detailes PS&Es |
| Right-of-Way | Additional land needed for project is purchased |
| Construction | State or local gov’t selects contractor, he/she then builds the project |
3 levels of planning
◼ State
◼ Regional (>50,000 pop.)
◼ Local
4 steps of convent’nl transport’n modeling
1. Trip generation
2. Trip distribution
3. Mode split
4. Trip assignment
exmpl scenario…
Trip generation: decision to travel for a specific purpose.
— “We need somewhere to go eat lunch, Chris!”
Trip distribution: choice of destination
— “Let’s go to Wendy’s; I hear they have a 4 for 4”
Mode choice: choice of travel mode
— “There’s 3 of us, let’s travel by car”
Network assignment: choice of route or path
— “My Google Maps says there’s a Wendy’s on 441. We can get there in 9 minutes”
trip generation
3 factors that influence trip productions & attraction
◼Density of land use affects production & attraction (Number of dwellings, employees, etc. per unit of land); Higher density usually = more trips
◼ Social and socioeconomic characters of users
influence production (Average family income, Education, Car ownership)
◼ Location (Traffic congestion, Environmental conditions)
Forecast # of trips that produced or attracted by each
area for a “typical” day,
Mon – Fri is usually focus only primarily
some basic terms
◼ Objective of a trip generation model is to forecast number of person-trios that shall begin from or end in each travel-analysis zone within the region for a typical day of said target year
◼ (HB) Home Based Trip – a trip where the home of trip-maker is either the origin or the destination
◼ (NHB) Non-Home Based Trip – a trip where the home is neither end of the trip
◼ Utility functions – what value does each user put on being able to travel (e.g. Utility of getting groceries is higher than going to the movies)
◼ Journey – this is a a one-way movement from a point of origin to a point of destinations
some definitions & factors
◼ Pi = f(z1, z2, z3, …), trip production for zone I,
◼ Ai = f(y1, y2, y3, …), trip attraction for zone I,
z factors include: (income, household structure, family size, car ownership, value of land, residential density)
y factors include: (industrial, commercial and other services, zonal employment, recreational resources)
trip gen. con’td definitions
◼ Trip Production – defined as a the home end of an HB trip, or as the origin of a NHB trip
◼ Trip Attraction – defined of the non-home-end of an HB trip or the destination of an NHB trip
◼ Trip Generation – often defined as the total number of trips generated by households in a zone be they HB or NHB
trip generation models
exmpl form:
Tj = b0 +b1z1j + b2z2j + … bnznj
◼ Tj is number of vehicle-based trips in a specified time period by household j
◼ Znj is characteristic n (e.g. income, employment, no. of members) of household j
◼ bn is a coefficient estimated from traveler survey data corresponding to characterstic n
trip distribution
T_{ij}=\frac{P_{i}(A_{j}\times F_{ij})}{\sum A_{j} \times F_{ij}}Tij = Trips from zone i to zone j
Pi = Trip production in zone i
Aj = Trip attraction in zone j
Fij = Effect of travel time & dinstance in zone i and zone j
mode choice (logit)
P_{ij}=\frac{e^{\text{transit utility}_{ij}}}{e^{\text{transit utility}_{ij}}+e^{\text{auto utility}_{ij}}}Pij = Probaility of using transit for a trip between Zone i to Zone j
Transity utility ij = f (transit level of service ij, income ij)
Auto utility ij = f (highway level of service ij, income ij)
growth-factor modeling
\begin{aligned}T_{i}&=F_{i}t_{i} \\ \\F_{i}&=\frac{f(P^{d}_{i},I^{d}_{i},C^{d}_{i})}{f(P^{c}_{i},I^{c}_{i},C^{c}_{i})}\end{aligned}Pij = Probaility of using transit for a trip between Zone i to Zone j
Transity utility ij = f (transit level of service ij, income ij)
Auto utility ij = f (highway level of service ij, income ij)
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