What is the relationship between the "y-intercept" on the graph and the instantaneous speed of the cart as it moved through the midpoint X1?

Average Velocity of Cart Through X1 Run #1 Set 0.78 Average Velocity Distance Between Gates Average Velocity (m/s) (m) Run #1 0.70 0.8 0.77- 2 0.74 0.6 3 0.74 0.4 0.76 Linear 0.75 0.2 mx + b 0.78 0.1 0.75 m = -0.0971 + 0.024 b = 0.782 + 0.012 6 r - -0.922 0.74 7 Average Velocity (m/s) 8 0.73 10 0.72 11 12 0.71 13 14 0.70- 15 16 0.69 17 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 18 Distance Between Gates (m) 19 20 Average Velocity of Cart Through X1