This style visualizes the surface=* and smoothness tags on highways. Currently it does the following:

• show highways that neither have surface=* or smoothness=* as solid black

• with the smoothness tag render a
  • blue thin line for smoothness=excellent
  • move from green (=good) to red (=impassable) for the rest of smoothness values, at the same time thicken the way and use dashed stiles as smoothness values

• with the surface tag render a
  • soft white halo (but only for values paved|asphalt|concrete|concrete_pavers)
  • for the rest render the value with text (light brown for dirt, ground, mud, light green for grass, etc..)

• do not render text for the most common values (excellent, good, asphalt, paved) as they are easily identifyable by color code and would distract from the problem zones

Best regards, cmuelle8

ps: if you need more styles, or have more professional needs, give me a holler via ​http://www.openstreetmap.org/message/new/cmuelle8

meta 
{
    title: "Surface";
    description: "Visualize surface=* of objects";
    version: "25_2019-07-18";
    author: "cmuelle8";
    
    watch-modified: true;
}

meta[lang=de]
{
    title: "Oberflächenbeschaffenheit";
    description: "Oberflächenbeschaffenheit, etwa von Wegen, hervorheben";
}

canvas
{
    background-color: #606060;
}



node
{
    symbol-shape: square;
    symbol-size: 2;
    symbol-stroke-color: white;
    symbol-stroke-opacity: 0.1;
}

node:connection
{
    symbol-shape: square;
    symbol-size: 2;
    symbol-stroke-color: white;
    symbol-stroke-opacity: 0.1;
}

way
{
    width: 1;
    color: #FF0000;
    opacity: 0.0;
}

way[landuse]:closed
{
    fill-color: yellow;
    fill-opacity: 0.02;
    z-index: -0.9;
}

way[natural]:closed
{
    fill-color: green;
    fill-opacity: 0.02;
    z-index: -0.9;
}

way[building]:closed
{
    width: 2;
    color: magenta;
    opacity: 0.1;
    fill-color: magenta;
    fill-opacity: 0.02;
    z-index: -0.8;
}

way[highway][area?]:closed
{
    width: 2;
    color: orange;
    opacity: 0.5;
    fill-color: orange;
    fill-opacity: 0.2;
    z-index: -0.5;
}

way[highway][!area]
{
    color: #202020;
    opacity: 1.0;
    z-index: 1.0;
}



way[highway][smoothness=impassable]
{
    width: 4;
    color: eval(rgb((7*0.142*(1-red(prop(color)))) + red(prop(color)), (1*0.142*(1-green(prop(color)))) + green(prop(color)), blue(prop(color))));
    dashes: list(3,5,2,2,5,3);
}

way[highway][smoothness=very_horrible]
{
    width: 4;
    color: eval(rgb((6*0.142*(1-red(prop(color)))) + red(prop(color)), (2*0.142*(1-green(prop(color)))) + green(prop(color)), blue(prop(color))));
    dashes: list(3,5,2,2,5,3);
}

way[highway][smoothness=horrible]
{
    width: 4;
    color: eval(rgb((5*0.142*(1-red(prop(color)))) + red(prop(color)), (3*0.142*(1-green(prop(color)))) + green(prop(color)), blue(prop(color))));
    dashes: list(3,5,2,2,5,3);
}

way[highway][smoothness=very_bad]
{
    width: 3;
    color: eval(rgb((4*0.142*(1-red(prop(color)))) + red(prop(color)), (4*0.142*(1-green(prop(color)))) + green(prop(color)), blue(prop(color))));
    dashes: list(3,5,2,2);
}

way[highway][smoothness=bad]
{
    width: 3;
    color: eval(rgb((3*0.142*(1-red(prop(color)))) + red(prop(color)), (5*0.142*(1-green(prop(color)))) + green(prop(color)), blue(prop(color))));
    dashes: list(4,4,2,2);
}

way[highway][smoothness=intermediate]
{
    width: 2;
    color: eval(rgb((2*0.142*(1-red(prop(color)))) + red(prop(color)), (6*0.142*(1-green(prop(color)))) + green(prop(color)), blue(prop(color))));
    dashes: list(7,5);
}

way[highway][smoothness=good]
{
    color: eval(rgb((1*0.142*(1-red(prop(color)))) + red(prop(color)), (7*0.142*(1-green(prop(color)))) + green(prop(color)), 0.4));
    dashes: list(10,2);
}

way[highway][smoothness=excellent]
{
    color: eval(rgb(red(prop(color)), green(prop(color)), 1.0));
}



way[highway][surface],
way[highway][smoothness]
{
    print-text: true;
    text-color: #B0E0EE;
    text-offset: 4;
}

way[highway][surface=unpaved],
way[highway][surface=dirt],
way[highway][surface=ground],
way[highway][surface=mud]
{
    text-color: #FFB0B0;
}

way[highway][surface=grass]
{
    text-color: #B0FFB0;
}

way[highway][surface=gravel],
way[highway][surface=fine_gravel],
way[highway][surface=pebblestone]
{
    text-color: #FFFFB0;
}

way[highway][surface=paved],
way[highway][surface=asphalt],
way[highway][surface=concrete],
way[highway][surface=concrete_pavers]
{
    print-text: false;
    casing-width: +2;
    casing-color: #7777AA;
    casing-dashes: eval(prop(dashes));
}

way[highway][smoothness=excellent],
way[highway][smoothness=good]
{
    print-text: false;
}

way[highway][smoothness][eval(prop(print-text))]
{
    font-size: 10;
    text: "smoothness";
    text-color: #EEE9BF;
    text-position: line;
    z-index: 1.0;
}

way[highway][surface][eval(prop(print-text))]
{
    font-size: 10;
    font-family: Arial;
    text: "surface";
    text-position: line;
    z-index: 1.0;
}

Styles_Surface-style.mapcss, Styles_Surface.zip

sample screenshot: