var route = {"color": "#FF0000", "fillOpacity": 1, "fillColor": "#FF0000", "weight": 3, "opacity": 1};

var myIcon = L.icon({iconUrl: 'circle.png', iconSize: [8, 8]})

var d1a = L.geoJSON(day01a, {onEachFeature: onEachFeature, style: route, pointToLayer: function (feature, latlng) {return L.marker(latlng, {icon: myIcon})}});
var d1a = L.geoJSON(day01b, {onEachFeature: onEachFeature, style: route, pointToLayer: function (feature, latlng) {return L.marker(latlng, {icon: myIcon})}});

var satellite   = L.tileLayer(mbUrl, {id: 'mapbox.satellite', attribution: mbAttr}),

street  = L.tileLayer(mbUrl, {id: 'mapbox.streets', attribution: mbAttr});

var map = L.map('map', {center: [37.792965, -111.485824], zoom: 5, layers: [street, d1a, d1b]});

var baseLayers = {"Satellite": satellite, "Street": street};
var overlays = {"Step 01": d1a, "Step 02": d1b};;

L.control.layers(baseLayers, overlays).addTo(map);

var routes = [d1a, d1b, d2a, d3a];
var step = 0;

var map = L.map('map', {center: [37.792965, -111.485824], zoom: 5, layers: [street, d1a]});

function cycle() {
    step += 1;
    if (step <= routes.length) {
        map.addLayer(routes[step]);
    }
}