M.O.L.* (1974)
This type for signage on the Amsterdam metro was designed in collaboration with a workgroup led by Pieter Brattinga. As a fair proportion of the signs are illuminated from within, using fluorescent tubes, the principles of optics were taken as the basis for the design. Whatever form an opening has — triangular, square or polygonal — the light shining through it onto a surface always tends to form a circle. M.O.L. is rounded throughout as a device to make illuminated lettering more even and legible. This was the first type design in which I started experimenting with the counters of letters (the spaces within the letters) by making them larger as a way of improving legibility.

* Mol is the Dutch word for a mole. The workgroup had come up with the idea of a mole as a mascot for the new underground railway. Outside every station in the city there would be a giant molehill with a mole pointing the way to the entrance with his nose. The idea was torpedoed by the city authorities, but we let it live on in the name of the typeface.