Highway traffic volume. Refer to the Transportation Engineering (Vol. 2, 2020) study that assessed the impact of snowfall and cold temperature on classified vehicle volume variation using five years of Weigh-in-Motion (WIM) data recorded at a highway near Leduc in Alberta, Canada, Exercise 12.75 (p. 760). Recall the total vehicle volume recorded as well as the snowfall categories (SC1 (SC1 = 0 cm), SC2 (0 6 SC2 6 = 3 cm), and SC3 (SC3 7 3 cm)). Say the study also considered temperatures (°C) in addition to total vehicle volume on the highway and the snowfall categories.

a. Write a first-order model (with no interaction) for mean total vehicle volume, E1y2, as a function of snow categories and temperature.

b. Refer to the model, part

a. For each snow category, express the change in total vehicle volume for each 1°C increase in temperature in terms of the model parameters.

c. Write an interaction model for mean total vehicle volume, E1y2, as a function of a snowfall category and temperature.

d. Refer to the model, part

c. For each snowfall category, express the change in total vehicle volume for each 1°C in temperature in terms of the model parameters.

e. Refer to the model, part

c. Illustrate the interaction with a graph.