Tailgating Model

This model allows students to examine safe driving conditions when one car is following another. Students build the simple model and then adjust the velocity, braking deceleration and following distance to create a graph of safe following distance vs. traffic velocity. Students analyze this graph and compare the rule they derive to those they've learned in driver's education classes.

 THE MODEL
 Vensim Version Vensim PLE Software Right-click to download the model Tailgate ModelVensim STELLA Version isee Player Software Right-click to download the model

[Diagram Level | Equations Level | Graphs ] ```Distance_Back_Car(t) = Distance_Back_Car(t - dt) + (Chg_Dist_Back) * dt
INIT Distance_Back_Car = 0
Chg_Dist_Back = Velocity_Back_Car*1.47
DOCUMENT:  1.47 converts mph back to ft/sec

Distance_Front_Car(t) = Distance_Front_Car(t - dt) + (Chg_Dist_Front) * dt
INIT Distance_Front_Car = Carlengths_Between*16
Chg_Dist_Front = Velocity_Front_Car*1.47
DOCUMENT:  1.47 converts mph back to ft/sec

Velocity_Back_Car(t) = Velocity_Back_Car(t - dt) + (- Decel_Back_Car) * dt
INIT Velocity_Back_Car = Initial_Velocity_Back
Decel_Back_Car = if time<(5+Rxn_Time_Back) then 0 else Decel_Rate_Back*0.682
DOCUMENT:  0.682 converts deceleration in ft/sec^2 to mph^2

Velocity_Front_Car(t) = Velocity_Front_Car(t - dt) + (- Decel_Front_Car) * dt
INIT Velocity_Front_Car = Initial_Velocity_Front
Decel_Front_Car = IF time<5 then 0 else Decel_rate_Front*0.682
DOCUMENT:  0.682 converts deceleration in ft/sec^2 to mph^2

Carlengths_Between = 4
Decel_Rate_Back = 28 {ft/sec^2}
Decel_rate_Front = 28 {ft/sec^2}
Initial_Velocity_Back = 45 {mph}
Initial_Velocity_Front = 45 {mph}
Rxn_Time_Back = 0.45 {sec}

Time Specs Settings
Standard: Range 0-12, dt = 0.25, Integration Method = Euler's

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