Challenge accepted:

~~~~ pikchr
    $laneh = 0.75

    # Draw the lanes
    down
    box width 3.5in height $laneh fill 0xacc9e3
    box same fill 0xc5d8ef
    box same as first box
    box same as 2nd box
    line from 1st box.sw+(0.2,0) up until even with 1st box.n \
      "Alan" above aligned
    line from 2nd box.sw+(0.2,0) up until even with 2nd box.n \
      "Betty" above aligned
    line from 3rd box.sw+(0.2,0) up until even with 3rd box.n \
      "Charlie" above aligned
    line from 4th box.sw+(0.2,0) up until even with 4th box.n \
       "Darlene" above aligned

    # fill in content for the Alice lane
    right
A1: circle rad 0.1in at end of first line + (0.2,-0.2) \
       fill white thickness 1.5px "1" 
    arrow right 50%
    circle same "2"
    arrow right until even with first box.e - (0.65,0.0)
    ellipse "future" fit fill white height 0.2 width 0.5 thickness 1.5px
A3: circle same at A1+(0.8,-0.3) "3" fill 0xc0c0c0
    arrow from A1 to last circle chop "fork!" below aligned

    # content for the Betty lane
B1: circle same as A1 at A1-(0,$laneh) "1"
    arrow right 50%
    circle same "2"
    arrow right until even with first ellipse.w
    ellipse same "future"
B3: circle same at A3-(0,$laneh) "3"
    arrow right 50%
    circle same as A3 "4"
    arrow from B1 to 2nd last circle chop

    # content for the Charlie lane
C1: circle same as A1 at B1-(0,$laneh) "1"
    arrow 50%
    circle same "2"
    arrow right 0.8in "goes" "offline"
C5: circle same as A3 "5"
    arrow right until even with first ellipse.w
    ellipse same "future"
    text "back online" "pushes 5" "pulls 3 & 4" with .n at last arrow

    # content for the Darlene lane
D1: circle same as A1 at C1-(0,$laneh) "1"
    arrow 50%
    circle same "2"
    arrow right until even with C5.w
    circle same "5"
    arrow 50%
    circle same as A3 "6"
    arrow right until even with first ellipse.w
    ellipse same "future"
D3: circle same as B3 at B3-(0,2*$laneh) "3"
    arrow 50%
    circle same "4"
    arrow from D1 to D3 chop
~~~~

There is a new construct (not found in legacy-PIC) where you can say
things like:  "arrow right until even with ...".  Very helpful for keeping
objects aligned.