Looks like the design of Matrix class could be improved. Here are some points:

1. Matrix is a template class, but is only instantiated for uint32_t (in fact it's UserCost, UserDuration and UserDistance, but all boil down to the same type).
2. The implementation is partly in source file, which requires explicit template instantiation (see:

   vroom/src/structures/generic/matrix.cpp

   Line 36 in 176f57a

   template class Matrix<UserCost>;

   ) to prevent linking errors. The instantation is for UserCost, which automatically works for UserDuration and UserDistance due to all three being an alias for uint32_t. Adding explicit instantiation for the latter two types for clarity results in compiler error (duplicate explicit instantiation of ‘class vroom::Matrix<unsigned int>’).
3. Trying to reuse the class for any other type is not possible due to linker errors.
4. The constructors could be cleaned up a bit.

I propose to leave Matrix as a template class but move the implementation entirely to the header file.