Development grid
Type of Cell (per column, along the road)
How the model works
This model projects how development spreads along a linear road corridor. Each of the 20 columns represents a segment of road; each of the 11 rows is a band of land parallel to it (5 above, the road itself at row 5, and 5 below). Row 5 is the "seed row" where inputs combine. Off-row cells inherit a decayed share of the adjacent Type of Cell value and a static Position-of-Cell field. The grid is then propagated forward by neighborhood averaging for as many generations as you pick.
1. Road sets the stage
Road type (highway → local) and length set two global weights. Higher-class shorter roads have more pull.
2. Settlements pull
Population at each end creates a linear gravitational pull that interpolates across the corridor.
3. Geometric decay
Position-of-Cell decays away from the road (×0.5 per row) and from the endpoints (×0.75 per column).
4. Junctions boost
Each cell's Type of Cell (straight, T-junction, full junction, endpoint) adds a value and leaks into adjacent rows.
5. Hard overrides
Already-built and Agglomeration cells lock at 1. Slope and Restriction lock at 0. These always win.
6. Propagation
Each next generation adds the neighborhood average to each cell. Moore uses 8 neighbors, von Neumann uses 4. Saturated cells (≥1) stay at 1.
7. Limit of growth
Two optional brakes on each cell. The S-curve (α) chokes inflow as value approaches 1, giving the classic slow-fast-plateau curve. The per-cell growth-rate decay caps each generation's growth at a fraction of the previous generation's growth (0.5 = halves every step). Both prevent cells from reaching 1.0 too quickly.