Dynamic Delivery Routes

A logistics company operates in a large city, represented as a weighted directed graph. Each node represents a location and each edge represents a road between locations with an associated travel time. However, due to road maintenance and temporary closures, certain roads may be unavailable on any given day.

You are given:

• An integer n representing the number of locations (nodes numbered from 1 to n).
• A list of edges where each edge is represented as a tuple (u, v, t), indicating a road from location u to location v with travel time t.
• A list of temporarily unavailable roads for the day, where each road is identified by its corresponding tuple (u, v). These roads should be ignored for that day.
• Two integers, start and destination, indicating the starting and ending locations.

Your task is to design and implement an efficient algorithm to compute the shortest travel time from the start location to the destination location, taking into account the unavailable roads. If there is no possible route under the given conditions, your program should indicate so.

Assume that the number of nodes can be up to 10^4 and the number of edges up to 10^5. Efficiency is important.

Write a function or method in the programming language of your choice that takes as input the graph details, the list of unavailable roads, and the start/destination nodes, and returns the shortest travel time or an indication that the destination is unreachable.

Feel free to include any assumptions or clarifications in your solution documentation.