Traffic:

Cars and Trucks

Background Information

The U.S. Interstate Highway System was established in 1956 by president Eisenhower. It was proposed as a way to provide for rapid movement of vehicles, both military and personal, for national defense.

Since that time, the system has been used primarily for personal and commercial travel.

In this activity students will:

• conduct their own traffic survey; and

they will become aware of:

• the relative use of the system by commercial and personal vehicles;
• the types of personal vehicles most commonly used;
• the relative impacts of each vehicle type on highways; and
• the relative impact to the categories of vehicles observed in these surveys.

Part 1: Introduction

On Saturday, April 8, 2000, at 2:30 p.m., on I-80 west of Lyman, WY, as we headed east, we counted semis, light trucks, and cars that passed us heading west for a 10 mile stretch.

We counted again, using the same procedure, at 6:30 and 7:30. Here are our findings:

After taking the second sample, we predicted the third sample would:

• have less traffic;
• have a greater percentage of semis.

Our reasoning was:

• It was later in the day, so fewer people would be driving.
• There would be more trucks in proportion to fewer cars.

Actual sample had:

• more traffic;
• a smaller percentage of trucks.

Directions: Complete either:

• 1
• 1 and 2
• 1, 2, and 3
• 2 and 3
• 1, 2, 3, and 4
• 1, 2, 3, 4, and 5
• 4 and 5

1. What may have been possible reasons for the difference between our prediction and the actual count?

2. Design your own technique for counting categories of vehicles. What will you base the count on?

• The time spent observing?
• The place where the counting was done?

3. After you count and record the numbers of vehicles, using a calculator or spreadsheet:

a. Calculate the possible number of vehicles per category per day for your location.

Vehicle Category	Number in 10 minutes	Number per Hour	Number per Day
Semi
Pickup
SUV
Car

b. If the average miles per gallon for each category of vehicle is semis 5; pickups 15; SUVs 20; cars 26:

• Calculate the amount of gas used by a vehicle in each category for a selected length of trip (example: 100 miles).
• Calculate the total amount of gas used by each category of vehicle in your sample.
• Calculate the total amount of gas used by all the vehicles you counted in your sample.

 

Total Gas Used: _________

c. Calculate:

• The total weight for each category of vehicle in your sample.
• The percentage of the total vehicle weight for your sample for each category of vehicle.

 

4. If a gallon of gasoline burned in a vehicle yields: 20 lbs CO2 and .05 lbs of NO calculate:

• The amount of each of these two types of emissions by one one vehicles in each category traveling 100 miles.
• The amount of each of these two types of emissions by all vehicles traveling 100 miles in each category in your sample.
• The total amount of each emission emitted by all vehicles in your sample.
• The percentage of the total amount of each pollutant emitted by each category in your sample.

5. Based on calculations for questions 3 and 4:

• What vehicle category is the most destructive to both highways and air quality?
• Which personal vehicle is the least destructive to both highways and air quality?

Teachers Notes

1. Possible reasons for the difference between our prediction and the actual count may have been:

• The sample was taken between two major cities, where there might be more auto traffic.
• The weather was beautiful.
• It was Saturday night; people going out.

2. Sampling techniques may vary.

3. A semi uses approximately 2.5 times as much gas as a light truck and 4.3 times as a much gas as a passenger cart to travel the same distance.

• A truck uses approximately 1.7 times as much gas as a passenger car.
• Figures will vary.

4. Our samples indicate that:

• semis release % of the pollutants produced compared compared to only 5 by personal vehicles.

5. Semis are the most destructive; passenger cars are the least.

Interdisciplinary Approach: Earth Science and math.