If you live in Maryland and you are en route to Delaware (but) you stop for gas or a burger while still in Maryland you are no longer en route to Delaware. You could be stopped by the police. It's my understanding Maryland's meaning of en route is to go DIRECTLY to your destination.
If you are referring to the federal Firearms Owners Protection Act, this wil be of no use in your home state. Carry has to be legal at both ends.
Example: going from Delaware to Vermont. Passing through New Jersey, new York, Connecticut and Massachusetts you would be good because carrying unloaded and in trunk is legal in both states. Maryland is not legal. This even though posessing an unloaded inaccesable handgun is illegal in those intermediate states. You may of course stop for gas or eat, but the firearm must remain unloaded in trunk. If vehicle does not have a trunk it must be away from the driver in a locked container.
In fact Delaware is the only state around here that you may transport a handgun in your vehicle without s license routinely. Pennsylvania, Maryland and Nee Jersey forbid transporting even an unloaded and inaccesable handgun without a license with some exceptions.