diff --git a/src/wsp_balsa/routines/io/nwp.py b/src/wsp_balsa/routines/io/nwp.py
index c992a9a..4487930 100644
--- a/src/wsp_balsa/routines/io/nwp.py
+++ b/src/wsp_balsa/routines/io/nwp.py
@@ -17,6 +17,7 @@
 
 import re
 import zipfile
+from io import IOBase, TextIOBase, TextIOWrapper
 from os import PathLike
 from pathlib import Path
 from typing import Hashable, List, Tuple, Union
@@ -47,26 +48,53 @@ def process_emme_eng_notation_series(s: pd.Series, *, to_dtype=float) -> pd.Seri
     return values * units
 
 
-def read_nwp_base_network(
-    nwp_fp: Union[str, PathLike],
+def _open_nwp(nwp_fp: Union[str, PathLike]) -> zipfile.ZipFile:
+    """Open a Network Package file for reading.
+
+    Helper which checks for existence of network package before opening.
+    """
+    nwp_fp = Path(nwp_fp)
+    if not nwp_fp.exists():
+        raise FileNotFoundError(f"Network Package file `{nwp_fp.as_posix()}` not found.")
+
+    return zipfile.ZipFile(nwp_fp)
+
+
+def _get_file_object(file_obj: Union[str, PathLike, IOBase]) -> TextIOBase:
+    """Get a file object which reads strings.
+
+    Helper method to gracefully handle reading files from str or Path filepaths,
+    as well as binary text files (such as the files returned by ``ZipFile.open``).
+    """
+    if isinstance(file_obj, TextIOBase):
+        return file_obj
+    if isinstance(file_obj, IOBase):
+        return TextIOWrapper(file_obj, encoding="utf-8")
+
+    fp = Path(file_obj)
+    if not fp.exists():
+        raise FileNotFoundError(f"File `{fp.as_posix()}` not found.")
+    return open(fp, "r", encoding="utf-8")
+
+
+def read_base_network_transaction(
+        network_transaction_file: Union[str, PathLike, IOBase]
 ) -> Tuple[pd.DataFrame, pd.DataFrame]:
-    """A function to read the base network from a Network Package file (exported from Emme using the TMG Toolbox) into
-    DataFrames.
+    """Read an EMME base network transaction.
 
     Args:
-        nwp_fp (str | PathLike): File path to the network package.
+        network_transaction_file: (str | PathLike | IOBase): Path to the network
+            transaction file, or a file object for a network transaction file.
 
     Returns:
-        Tuple[pd.DataFrame, pd.DataFrame]: A tuple of DataFrames containing the nodes and links
+        Tuple[pd.DataFrame, pd.DataFrame]: A tuple of DataFrames containing the nodes and links.
     """
-    nwp_fp = Path(nwp_fp)
-    if not nwp_fp.exists():
-        raise FileNotFoundError(f"File `{nwp_fp.as_posix()}` not found.")
 
-    header_nodes, header_links, last_line = None, None, None
-    with zipfile.ZipFile(nwp_fp) as zf:
-        for i, line in enumerate(zf.open("base.211"), start=1):
-            line = line.strip().decode("utf-8")
+    with _get_file_object(network_transaction_file) as open_file:
+        # Determine start of nodes and links
+        header_nodes, header_links, last_line = None, None, None
+        for i, line in enumerate(open_file, start=1):
+            line = line.strip()
             if line.startswith("c"):
                 continue  # Skip comment lines
             if line.startswith("t nodes"):
@@ -87,8 +115,10 @@ def read_nwp_base_network(
             "Data3": float,
             "Label": str,
         }
+
+        open_file.seek(0)
         nodes = pd.read_csv(
-            zf.open("base.211"),
+            open_file,
             index_col="Node",
             dtype=data_types,
             skiprows=header_nodes,
@@ -104,8 +134,9 @@ def read_nwp_base_network(
 
         # Read links
         n_rows = last_line - header_links - 1
+        open_file.seek(0)
         links = pd.read_csv(
-            zf.open("base.211"),
+            open_file,
             index_col=["From", "To"],
             skiprows=header_links,
             nrows=n_rows,
@@ -136,47 +167,38 @@ def read_nwp_base_network(
     return nodes, links
 
 
-def read_nwp_exatts_list(
-    nwp_fp: Union[str, PathLike],
+def read_exatts_list(
+    exatts_file: Union[str, PathLike, IOBase],
     **kwargs,
 ) -> pd.DataFrame:
-    """A function to read the extra attributes present in a Network Package file (exported from Emme using the TMG
-    Toolbox).
+    """Read extra attributes definitions exported from EMME.
 
     Args:
-        nwp_fp (str | PathLike): File path to the network package.
+        exatts_file (str | PathLike | IOBase): Path to the exatts file,
+            or a file object for an exatts file.
         **kwargs: Any valid keyword arguments used by ``pandas.read_csv()``.
 
     Returns:
         pd.DataFrame
     """
-    nwp_fp = Path(nwp_fp)
-    if not nwp_fp.exists():
-        raise FileNotFoundError(f"File `{nwp_fp.as_posix()}` not found.")
-
     kwargs["index_col"] = False
     if "quotechar" not in kwargs:
         kwargs["quotechar"] = "'"
 
-    with zipfile.ZipFile(nwp_fp) as zf:
-        df: pd.DataFrame = pd.read_csv(zf.open("exatts.241"), **kwargs)
+    with _get_file_object(exatts_file) as open_file:
+        df: pd.DataFrame = pd.read_csv(open_file, **kwargs)
         df.columns = df.columns.str.strip()
         df["type"] = df["type"].astype("category")
 
     return df
 
 
-def _base_read_nwp_att_data(
-    nwp_fp: Union[str, PathLike],
-    att_type: str,
+def _base_read_extatts(
+    exatts_file: Union[str, PathLike, IOBase],
     index_col: Union[str, List[str]],
     attributes: Union[str, List[str]] = None,
     **kwargs,
 ) -> pd.DataFrame:
-    nwp_fp = Path(nwp_fp)
-    if not nwp_fp.exists():
-        raise FileNotFoundError(f"File `{nwp_fp.as_posix()}` not found.")
-
     if attributes is not None:
         if isinstance(attributes, Hashable):
             attributes = [attributes]
@@ -188,8 +210,8 @@ def _base_read_nwp_att_data(
     if "quotechar" not in kwargs:
         kwargs["quotechar"] = "'"
 
-    with zipfile.ZipFile(nwp_fp) as zf:
-        df: pd.DataFrame = pd.read_csv(zf.open(f"exatt_{att_type}.241"), **kwargs)
+    with _get_file_object(exatts_file) as open_file:
+        df: pd.DataFrame = pd.read_csv(open_file, **kwargs)
         df.columns = df.columns.str.strip()
         for col in df.columns:
             if is_string_dtype(df[col]):
@@ -202,6 +224,108 @@ def _base_read_nwp_att_data(
     return df
 
 
+def read_node_extra_attributes(
+    exatts_file: Union[str, PathLike, IOBase],
+    *,
+    attributes: Union[str, List[str]] = None,
+    **kwargs,
+) -> pd.DataFrame:
+    """Read node attributes exported from EMME.
+
+    Args:
+        exatts_file (str | PathLike | IOBase): Path or file object corresponding to
+            an extra attributes file.
+        attributes (str | List[str], optional): Defaults to ``None``.
+            Names of node attributes to extract.
+            Note that ``'inode'`` will be included by default.
+        **kwargs: Any valid keyword arguments used by ``pandas.read_csv()``.
+
+    Returns:
+        pd.DataFrame
+    """
+    return _base_read_extatts(exatts_file, "inode", attributes, **kwargs)
+
+
+def read_link_extra_attributes(
+    exatts_file: Union[str, PathLike, IOBase],
+    *,
+    attributes: Union[str, List[str]] = None,
+    **kwargs,
+) -> pd.DataFrame:
+    """Read link attributes exported from EMME.
+
+    Args:
+        exatts_file (str | PathLike | IOBase): Path or file object corresponding to
+            an extra attributes file.
+        attributes (str | List[str], optional): Defaults to ``None``.
+            Names of link attributes to extract.
+            Note that ``'inode'`` and ``'jnode'`` will be included by default.
+        **kwargs: Any valid keyword arguments used by ``pandas.read_csv()``.
+
+    Returns:
+        pd.DataFrame
+    """
+    return _base_read_extatts(exatts_file, ["inode", "jnode"], attributes, **kwargs)
+
+
+def read_transit_line_extra_attributes(
+    exatts_file: Union[str, PathLike, IOBase],
+    *,
+    attributes: Union[str, List[str]] = None,
+    **kwargs,
+) -> pd.DataFrame:
+    """Read transit line attributes exported from EMME.
+
+    Args:
+        exatts_file (str | PathLike | IOBase): Path or file object corresponding to
+            an extra attributes file.
+        attributes (str | List[str], optional): Defaults to ``None``.
+            Names of transit line attributes to extract.
+            Note that ``'line'`` will be included by default.
+        **kwargs: Any valid keyword arguments used by ``pandas.read_csv()``.
+
+    Returns:
+        pd.DataFrame
+    """
+    return _base_read_extatts(exatts_file, "line", attributes, **kwargs)
+
+
+def read_nwp_base_network(
+    nwp_fp: Union[str, PathLike],
+) -> Tuple[pd.DataFrame, pd.DataFrame]:
+    """A function to read the base network from a Network Package file (exported from Emme using the TMG Toolbox) into
+    DataFrames.
+
+    Args:
+        nwp_fp (str | PathLike): File path to the network package.
+
+    Returns:
+        Tuple[pd.DataFrame, pd.DataFrame]: A tuple of DataFrames containing the nodes and links
+    """
+    with _open_nwp(nwp_fp) as zf:
+        base_transaction_file = zf.open("base.211")
+        return read_base_network_transaction(base_transaction_file)
+
+
+def read_nwp_exatts_list(
+    nwp_fp: Union[str, PathLike],
+    **kwargs,
+) -> pd.DataFrame:
+    """A function to read the extra attributes present in a Network Package file (exported from Emme using the TMG
+    Toolbox).
+
+    Args:
+        nwp_fp (str | PathLike): File path to the network package.
+        **kwargs: Any valid keyword arguments used by ``pandas.read_csv()``.
+
+    Returns:
+        pd.DataFrame
+    """
+    with _open_nwp(nwp_fp) as zf:
+        exatts_file = zf.open("exatts.241")
+        return read_exatts_list(exatts_file, **kwargs)
+
+
 def read_nwp_node_attributes(
     nwp_fp: Union[str, PathLike],
     *,
@@ -219,7 +343,9 @@ def read_nwp_node_attributes(
     Returns:
         pd.DataFrame
     """
-    return _base_read_nwp_att_data(nwp_fp, "nodes", "inode", attributes, **kwargs)
+    with _open_nwp(nwp_fp) as zf:
+        ea_file = zf.open(f"exatt_nodes.241")
+        return read_node_extra_attributes(ea_file, attributes=attributes, **kwargs)
 
 
 def read_nwp_link_attributes(
@@ -239,7 +365,9 @@ def read_nwp_link_attributes(
     Returns:
         pd.DataFrame
     """
-    return _base_read_nwp_att_data(nwp_fp, "links", ["inode", "jnode"], attributes, **kwargs)
+    with _open_nwp(nwp_fp) as zf:
+        ea_file = zf.open(f"exatt_links.241")
+        return read_link_extra_attributes(ea_file, attributes=attributes, **kwargs)
 
 
 def read_nwp_transit_line_attributes(
@@ -260,7 +388,9 @@ def read_nwp_transit_line_attributes(
     Returns:
         pd.DataFrame
     """
-    return _base_read_nwp_att_data(nwp_fp, "transit_lines", "line", attributes, **kwargs)
+    with _open_nwp(nwp_fp) as zf:
+        ea_file = zf.open(f"exatt_transit_lines.241")
+        return read_transit_line_extra_attributes(ea_file, attributes=attributes, **kwargs)
 
 
 def read_nwp_traffic_results(