The border is open between 7am and 7.30pm. The trip is only about three hours from Nigeria. The main roads from most surrounding countries are tarred and in fair condition, so driving yourself is also an option.
Minibuses are slower, but cost about a quarter of the taxi rate.
The entire trip takes about nine hours, and trains go each way every morning. Every second day there's an evening service with a sleeper coach. Hire cars are available from Cotonou airport or the Sheraton. There is a daily charge which is added to a distance rate. Petrol is extra.