void printLights(boolean[] llights, boolean[] rlights)
    {
        System.err.println("##### Setting traffic lights #####");

        for (int i = 0; i != nsegments + 1; ++i) {
            if (i != 0 && llights[i-1] == true)
                System.err.print("<");
            else
                System.err.print(" ");
            System.err.print("=");
            if (i != nsegments && rlights[i] == true) 
                System.err.print(">");
            else
                System.err.print(" ");
            if (i != nsegments) {
                int nspace = 4 * nblocks[i] - 1;
                printSpaces(nspace);
            }
        }
        System.err.println();
    }