Transportation Planning - Examples & Applications

Example: Gravity Model Calculation

Let's perform a simplified Trip Distribution calculation using the Gravity Model.

Example

Problem Statement: Traffic Analysis Zone 1 produces 1,000 trips daily (

P_1 = 1000

). Zones 2 and 3 are the only available destination zones, attracting 2,000 (

A_2

) and 3,000 (

A_3

) trips respectively.

The travel time from Zone 1 to Zone 2 ( $t_{12}$ ) is 10 minutes.
The travel time from Zone 1 to Zone 3 ( $t_{13}$ ) is 20 minutes.
Assume the friction factor function is $F_{ij} = 1/t_{ij}^2$ and all $K$ factors are 1.0.

Determine the number of trips distributed from Zone 1 to Zone 2 (

T_{12}

) and Zone 1 to Zone 3 (

T_{13}

Solution: Gravity Model Calculation

0 of 4 Steps Completed

Example: Trip Generation Calculation

Trip generation determines the number of trips that will begin or end in a specific traffic analysis zone (TAZ).

Example

Problem Statement: A new residential development is planned for TAZ 1. It will contain 200 households. On average, each household will own 1.5 cars. A transportation planner uses the following linear regression model to estimate the number of trips generated (

T_i

) per day by a zone:

T_i = 0.5 + 2.1(HH) + 3.5(Cars)

Calculate the total number of trips generated by TAZ 1 per day.

Given:

Number of households ( $HH$ $H H$ ) = 200
- Total cars in the zone ( $Cars$ ) = $200 \times 1.5 = 300$
- Trip generation model: $T_i = 0.5 + 2.1(HH) + 3.5(Cars)$

Step-by-Step Solution

0 of 2 Steps Completed

Example: Mode Choice Analysis

Mode choice (Modal Split) predicts the probability that an individual will choose a specific mode of transportation based on utility.

Example

Problem Statement: Commuters traveling from a suburb to downtown can choose between driving (Auto) or taking a bus (Transit). A logit model estimates the utilities of these modes as:

Utility of Auto ( $U_A$ ) = -1.2
Utility of Transit ( $U_T$ ) = -2.5

Calculate the probability that a commuter will choose to drive using the multinomial logit model formula. If there are 5,000 daily commuters, how many are expected to drive?

Given: The probability (

P_m

) of choosing mode

m

is given by:

P_m = \frac{e^{U_m}}{\sum e^{U_k}}

$U_A = -1.2$
$U_T = -2.5$
Total Commuters ( $N$ ) = 5000

Step-by-Step Solution

0 of 3 Steps Completed

Example: Route Assignment (All-or-Nothing)

Traffic assignment allocates the expected trips between origins and destinations onto the actual transportation network routes.

Example

Problem Statement: A transportation network has two possible routes connecting Node A (Origin) to Node B (Destination). Route 1 has a free-flow travel time of 15 minutes, and Route 2 has a free-flow travel time of 20 minutes. There are 1,200 vehicles moving from Node A to Node B. If an "All-or-Nothing" assignment model is used, determine how the traffic is assigned to the network.

Given: The All-or-Nothing assignment model assigns all traffic demand to the single route with the shortest travel time, regardless of capacity constraints or congestion.

Step-by-Step Solution

0 of 2 Steps Completed

PreviousTransportation Planning - Theory & Concepts

Quiz Me

NextHighway Geometric Design - Theory & Concepts