Task: Question Answering
Input (English): Passage: From the colonizers' perspective, Carabane's position at the mouth of the river was an undeniable asset. In the 20th and 21st centuries, in terms of trade and tourism issues, this location is more of a disadvantage because it effectively separates the island from the rest of the country.
While a direct route by sea has not been available since the sinking of the Joola, the traveller from Dakar may use various other means of transportation in order to arrive in Basse Casamance. Some national roads connect to Ziguinchor, down the N1 to Kaolack. The N4 and N5 roads cross the Gambia (both the country and the river), the former running through Nioro du Rip to Farafenni, and the latter crossing the river to Banjul. The two roads merge in Bignona before descending to Ziguinchor. However, traffic is forbidden on both roads between 7 p.m. and 10 a.m., and the routes are subject to frequent accidents and constant demining operations. Alternatively, it is possible to travel by plane to the airport in Ziguinchor or Cap Skirring, or to travel by boat to one of these locations. Reaching Carabane from either town is relatively straightforward.By boat, the distance between Dakar and Carabane is 265 kilometres (143 nmi), although Ziguinchor is only 48 kilometres (30 mi) away. Before the launch of the Joola, other boats, mostly well-worn ones, made the connection: first Cap Skirring, then the Casamance Express, and then Island Karabane. In January 1991, a brand new ferry went into operation. Like its predecessors, it connected Dakar to Ziguinchor, stopping near Carabane where canoes could reach the island. On September 26, 2002, 180 extra passengers boarded the already overloaded ship at this stop, and a few hours later, the Joola sank. For security reasons, the Joola's successor, the Wilis, stopped calling at Carabane, to the great displeasure of the inhabitants. Tourists became rare after that, and from time to time, inhabitants of the island found it necessary to move to Dakar or Ziguinchor. Significant modifications to the MV Aline Sitoe Diatta, which replaced the Wilis in March 2008, were considered to allow it to stop safely at the island, and the construction of a berth was announced. Souleymane Ndéné Ndiaye, who later became Prime Minister of Senegal, laid the first stone of the berth in July 2008, and the entire construction project was financed by the Senegalese government at an estimated cost of 12 billion West African CFA francs. On April 26, 2014, the MV Aline Sitoe Diatta stopped at the Carabane berth for the first time, improving transportation for locals and tourists. As of 2015, the ferry stops at Carabane four times each week in the middle of its trips between Dakar and Ziguinchor. 
Question: What routes are subject to frequent accidents and constant demining operations?
Output (English): N4.