the distance between two train stations is 30 km. a locomotive starting from one station gave the train an acceleration that made it reach 72km/h in 40seconds and this acceleration continued until the speed of the train reached 108km/h. This speed was maintained until brakes were applied to eventually bring the train to a stop at the second station under a uniform deceleration of 2m/s^2. How long did the entire journey take?​

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero.