How Mandatory are 'Mandatory' Lane Changes? An Empirical Study on the Costs of Missing Freeway Exits

Recently published:

• Wang, Zhaohan, Ramezani, M, and Levinson, D. (2024) How Mandatory are 'Mandatory' Lane Changes? An Empirical Study on the Costs of Missing Freeway Exits. Transportation Research part B. Volume 186, August 2024, 102994 [doi]

Highlights

• We question the concept of mandatory lane change by quantifying the cost of not making a lane change for tactical routing.

• Using probability theory and stochastic geometry, we formulate an analytical framework that models exit-missing costs.

• We conduct simulation study on the costs of missing freeway exits for the top 50 metropolitan regions in the US.

• We analyse the additional time and distance costs for missing an exit using GPS data from the Minneapolis - St. Paul metropolitan area.

Abstract

Lane changing, recognised as one of the most intricate manoeuvres in road traffic, has attracted extensive scholarly interest. To date, the concept of lane change has been categorised into two distinct classifications, namely mandatory and discretionary. Mandatory lane changes (MLCs) are often regarded as absolute, implying that the possibility of not executing the lane change is frequently disregarded. This paper questions this widely accepted proposition by evaluating the costs of neglecting an MLC. Specifically, we examine the costs associated with not making MLCs for exiting freeways, effectively quantifying the cost of missing such exits. The core of this study involves a dual approach comprising an analytical model for the costs of missing exits alongside an empirical analysis of two GPS datasets from the Minneapolis - St. Paul metropolitan area. The performance of the analytical model is validated by cross-referencing it against exit-missing costs from the top 50 metropolitan areas in the US. Regarding the empirical study, it was found that while both time and distance costs are associated with missing exits, the magnitudes of these costs are not substantial. The results obtained in this study offer novel insights into the nature of MLC, and we argue that future models should consist of discretionary (DLC), mandatory (MLC), and expedient (ELC) lane changes. Moreover, the analytical model developed in this study can be integrated into the trade-off function of an ELC model, enabling drivers to bypass their intended exit when needed.

Fig. 6. Distributions of the time cost of missing exits and corresponding CDFs. Cost is calculated by subtracting the travel time of the alternative route from the travel time of the original route. Blue plots correspond to samples without the SP constraint in place. Green plots correspond to samples with the 10% SP constraint. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)