Context: The heavy vehicles market requires increasingly more new software functions, which means that the embedded systems in vehicles are growing in size and complexity. To stay competitive, OEMs must develop multiple vehicle models with the same embedded systems, which requires variant management for proper behavior in different configurations.

Objective: We explore how different solutions to variant management impact the architectural maintainability of embedded systems. We study compile-time and build-time solutions w.r.t. their complexity.

Methods: We conduct a case study at Scania CV AB, an OEM in the heavy vehicle segment. Two large embedded systems controlling complex hardware were chosen as units of analysis.

Results: We found that the use of software product lines greatly decreased the complexity of system components. However, other customization approaches were found to increase the component complexities in the studied systems. Dependencies between components were analyzed and we found evidence of increased component coupling as a result of splitting components in a layered architecture approach, reducing the complexity within a component, but trading it with higher complexity on an architectural level.

Conclusions: These findings suggest that variant management approaches, while enhancing customization, affects maintainability. We found that the importance of balancing variant flexibility with architectural simplicity to mitigate long-term maintenance challenges. There seems to be a total amount of complexity that cannot be reduced, only moved around, and the key issue for developers and architects is to understand how to find a balance.