2D Road animation

I am animating a road which will be used in the analysis of a half car suspension model. At the moment the plot follows the road as it is being generated. What I want to do is plot the car in the middle of the plot and pull the road from right to left underneath the car.

    for t = 1:200

    r = road(t);
    R(t,:) = r;
%     pause(.05)
    set(line,'YData',R);  %# Update the y data of the line
    drawnow                %# Force the graphics to update immediately
    ylim([-1 1])
    xlim([t-5 t+5])

    end 

 figure; plot(R,'k');
 ylim([-1 1])

Does anyone have any suggestions on how to, rather than follow the road, have it come across the figure. Any help is much appreciated.

[James Murphy]

The road function is as follows,

    function [x] = road(t)
    % ROAD takes in time t and outputs height x.
    % road produces a step at t = 50s, undulation at t=100 and random road at
    % t>150.
    if t < 50
    x = 0;
    return
    elseif t >=50 && t < 100
    x = 0.05;
    return
    elseif t>=100 && t<150
    % x = 0.05 + 0.025*(0.4*sin(t));
    % x = (.05*sin(f*[1:.1:126]))+.05;
    x = 0.05*sin(0.25*t) + 0.05;
    return
    else
    x = 0.05 + 0.025*rand(1);
    return
    end