Roads, gates and access

A layout is only buildable if a service vehicle — and in the worst case a fire crew — can reach every piece of equipment. The solver treats access as a first-class constraint: it lays the road network before packing equipment, and it verifies reach on every candidate layout before showing it to you.

The perimeter ring (default)

With the default road topology, an access road loops just inside the boundary setback. Equipment fills the area inside the ring. The gate connects through the fence onto the ring, so the whole network is drivable from the entrance.

On a slanted or tapered parcel, the packed field is centered within the ring: rather than leave the equipment hugging one road with a wide empty strip against the opposite one, the solver slides the field to equalize the clearance to the two facing roads on each axis. Capacity is unchanged — the field moves as one rigid block, it is never re-packed. Single-block sections placed in the leftover space along the fence are not counted in that balance, and may keep their position while the field slides, as long as every clearance still holds.

Interior roads appear only where needed: when a site is large enough that equipment in the middle would sit too far from any road, the solver cuts the area into zones with a road between them. The threshold is the vehicle reach setting — a zone flanked by roads may be up to twice the reach across, since a vehicle can serve it from either side. Small sites get no interior roads at all: the ring plus the equipment's own service aisles are the access paths, and cutting a road through a small site would only cost capacity.

An interior road does not sit at a fixed spot between two zones. The solver moves the equipment and the roads together until each road sits at the required clearance from the equipment beside it. The space this frees collects at one end of the site, where another BESS section or the E-house can use it.

Road width is configurable (3 m default). The effective width is never below the drivable-lane minimum of your access settings, so a reserved road is always one a real vehicle can use.

Drive-through

Drive-through replaces the perimeter ring with one road between two gates — an entry and an exit: straight when the gates align, bent to follow them otherwise. Every bend is a curve a truck can drive, on the vehicle turning radius — both edges of the road follow it, and equipment keeps its normal road clearance from it. Where the road has to turn back on itself in less room than a turning circle, it ends that leg in a turning loop and comes back. There are no side roads, feeders or stubs: the drive is the only pavement on the site. The road leaves each gate head-on, square to the fence, before it turns, so the entrance is never a hard turn onto the fence line — even when a gate sits close to a corner. Where the fence is not square to the internal road, the entrance is one continuous curve: a straight through the gate (at least one road width, its length chosen with the route to pack the site best), then a sweep onto the internal road at the vehicle turning radius. Equipment, locked equipment included, keeps its normal road clearance from the curve. A gate tucked so far into a corner that no entrance fits there moves a few meters along its fence to the nearest spot where one does. A gate pressed so far into a tight corner that no drive can get out of it moves along its own fence — never round the corner — by a few road widths until one can. Only where no curved entrance fits the site at all does the drive keep a straight entrance, rather than leave you without a layout. Two gates that sit almost in line (less than 10 m apart, or two road widths on wider roads) get a straight drive: the second gate slides along its fence onto the first gate's line, so the road never kinks at a gate. Two gates on the same spot, crammed into the same corner, or almost in line on the same fence edge, share one entrance. A road with one entrance is a dead end, so it ends in a turnaround: a paved circle sized by the turning radius, set to one side of the road where the road runs close to a fence. The International Fire Code requires one on any dead-end fire access road longer than 150 ft (45.7 m); a turnaround on a shorter one is good practice — delivery and replacement trucks do not have to reverse out — and your local fire official may require it anyway. A smaller turning radius in Site details gives a smaller circle. Where the circle cannot fit straight ahead of the entrance — an entrance close to a sharp corner — the road turns once to reach a spot where it does. Only where no turnaround fits anywhere does the road stay a short dead end, no longer than the dead-end limit.

The equipment is planned along the drive: sections sit in bands beside each leg of the road, on both sides, and on the rest of the land within the vehicle reach of the road, including around and beyond the turning circle of a dead-end drive. Every unit stays within reach, with the E-house beside it near the grid connection. Land beyond reach of the drive stays empty — on a large site that is a real share of the parcel, and the capacity figure shows it; choose the perimeter ring when you want the whole site filled. Each option keeps one section type in one orientation where that holds within 15% of the densest layout. Both gates move from the Gate sliders, and the gate opening matches the road width. Moving one gate never moves the other: only the gate you are dragging may be adjusted — slid onto the other gate's line when the two nearly align, or along its fence to the nearest spot a road can reach — and its slider follows to where it was placed. It suits sites where traffic should pass through rather than loop — a delivery route during construction, or an AHJ that requires two points of egress.

No road

The Roads picker also offers No road: no ring, no interior roads. Zones are separated by the fire-safety distance instead of fire roads, and the service aisles between equipment rows become the access paths. On small and narrow parcels this recovers substantial capacity — a 3 m road band along each edge of a shallow site can consume a third of its usable depth.

No road does not mean no access. The solver still:

• reserves a clear apron inside the gate — one drivable width deep — so the entrance never opens straight into equipment, and keeps the E-house away from it;
• verifies that the aisle network actually reaches every unit from the gate, at the drivable width your access settings require.

Whether aisles-as-access is acceptable is a project-level decision — it suits fenced compounds where maintenance access is by light vehicle, and it will not suit sites where the authority requires a dedicated apparatus road. The tool shows you the capacity consequence of each choice; the requirement itself comes from your project.

Small parcels: roads omitted automatically

A perimeter ring takes a road width of buildable depth off all four sides. On a parcel too small for that ring, requiring it would leave nothing to place — so rather than report the site as unbuildable, the solver retries once with the internal roads removed and shows the note "Roads omitted — site too small for an internal road." The equipment still sits behind your configured boundary setback — nothing is pushed onto the fence — and the same aisle-reach checks apply. Only when a parcel is too small to fit any equipment even with roads omitted does the tool ask you to draw a larger area.

Vehicle reach

The access settings in Site details define what counts as reachable:

• Drivable width — the minimum clear width for a lane to count as a road.
• Reach — the maximum distance from any equipment to a drivable, gate-connected lane.
• Turning radius — the vehicle's turning radius at the road centerline: the curve a drive-through entrance sweeps on where the fence is not square to the internal road, and the size of a turnaround. 7 m by default — the smallest that still gives the 16.8 m turning circle a UK fire engine needs (the International Fire Code leaves the value to the local fire official) — 6–20 m, shown in feet when the map is set to feet.

Defaults suit common practice, and all three are tunable to your authority's figures. The solver uses reach twice: forward, to decide where interior roads are needed (or, with a drive-through, how far from the road equipment may stand), and backward, to verify every candidate — a layout with unreachable equipment is discarded before you ever see it.

The gate

The Gate slider moves the vehicle gate anywhere on the fence; the fence opens at the gate and the entrance connects to the internal network — the ring road, or the gate apron when no roads are selected. Gates near a boundary corner slide along the fence just enough to fit the opening on one straight segment. The gate position also feeds the access verification: reach is always measured from the gate, so moving it can change which layouts are valid on a tight site.